Few works deal specifically with the costume of the general population on the Island. Moore  has a section, based on entries in Encyclopedia Britannica dealing with Ireland which purports to describe the pre-Norse costume but would appear to make no further mention of costume.
The work by McClintock  was probably the first attempt to examine the costume of the Gaelic people and was picked up by B. Megaw as the basis for his paper of 1944 since which time there would appear to be no further paper dealing with costume.
The Isle of Man with its unique mixture of Gael, Norse and later English can be supposed to have followed trends in each.
Taken from Megaw and McClintock :
The earliest records of Gaelic dress come from a variety of Irish sources older than the AngloNorman invasion. These sources include early writings and heroic tales, carvings on ninth- and tenth-century stone crosses, figures on metal shrines, as well as marginal drawings in the famous Book of Kells. From these we learn that before the invasion of A.D. 1170, and probably for centuries earlier, two distinct forms of costume were worn by men: one was definitely aristocratic, while the other was in use among the ordinary people and fighting men.
(i) Chieftains and men of rank wore two main garments: a smock-like tunic known as leine (pronounced layna), long enough to reach the ankles unless drawn up through a belt. The leine was generally made of linen, but was occasionally of silk; it might be either white or dyed and was often decorated with a band of embroidery round the bottom hem. Over this was worn a large woollen cloak, or mantle, called a brat which had no sleeves and was shaped something like a bishop's cope. This mantle was usually a bright colour such as crimson, blue or green with a fringe round its edge, and was fastened on the breast with a metal brooch or pin.
(ii) The lower classes and ordinary fighting men wore a short and sometimes sleeveless jacket, with a shorter version of the mantle, and tight ' trews ' Gaelic triubhas (a word from which the English 'trousers' is derived) Trews were not unlike the medieval 'trunk hose' of Western Europe: when of full length they reached to the instep and were fastened by a strap beneath the sole of the foot but they were often much shorter, ending just below or even above the knee.
Women's dress, so far as our scanty evidence goes, seems to have consisted of a mantle like that of the men, worn over a leine which reached almost to the ground. While men usually went bare-headed with long hair, women probably wore a linen wrapping round the head as they did in later times.
They go on to conjecture that these two styles of costumes have different origins - the aristocratic one being based on earlier Roman models whilst that of the lower classes is the original Celtic dress (breeches being also worn by continental Celts).
A description of Viking women's costume is given by Judith Jesch :
The most characteristic items of female jewelry are the pairs of oval brooches (sometimes called tortoise brooches, from their shape), usually made of bronze, found in many female graves from the Viking Age. ... These brooches must not be thought of as purely decorative objects, they served the highly practical purpose of keeping a woman's dress up! In fact, apart from their diagnostic value in identifying female graves, oval brooches can tell us a great deal about the dress of Viking Age women, when they and the textile remains preserved around them are subjected to detailed archaeological analysis. Were it not for the brooches, we would in fact know very little about what the well-dressed woman wore in this period.
Textiles do not normally survive very well in the ground, unless there are very special conditions. However, there are quite large numbers of textile fragments found in association with the oval brooches and other metal objects. Some are still attached to the brooch and have been protected from disintegration by its proximity. In other cases, the textile has disappeared but has left an impression on the metal of the brooch. Painstaking research, particularly by Agnes Geijer and Inga Hagg on the textiles of Birka, has helped to establish what fabrics the brooches were attached to. On this basis, it has been possible to reconstruct the entire habit of the women of Birka, even though no whole dress is preserved. Finds from elsewhere, particularly Hedeby, confirm that fashions were essentially the same throughout the Viking world. Normally, a woman would wear an outfit consisting of two or three layers. First, a shift or underdress was worn. This could be of linen or wool, had sleeves, and was sometimes pleated and gathered at the neck. The neck opening was usually held together by a small disc brooch. Over the shift, the woman wore a strapped gown, or overdress. This was basically a rectangular piece of material (usually wool) wrapped around the woman's body and reaching to her armpits. Holding the gown up were looped straps over the woman's shoulders which were sewn on at the back and which were joined to smaller loops sewn on to the front by means of the two oval brooches, the pins of which passed through the loops. Thus, the term 'brooch' is something of a misnomer, since their function was more like that of a buckle. The strings of beads found in many women's graves could be hung between the oval brooches. Pendants of amber, jet or silver could also be strung between the beads at intervals: this is where the woman from Bjorke may have hung her Anglo-Saxon book mount. Here also the woman newly converted to Christianity could wear a small silver cross. Useful implements, like scissors and knives, could also hang from the brooches on straps or rings. Another garment which could be worn in addition to the basic shift and gown was a tunic worn between them, known from Birka and clearly of oriental inspiration. The better-dressed woman would have her tunic decorated with bands of tablet-woven braid of linen or silk, often with a metal weft for a particularly luxurious effect. Over all these garments, for outdoors, a woman might wear a sleeved caftan or a cloak, also held together by a brooch or pin. There was more variation in this fastening, it could be a disc brooch, a trefoil brooch, an equal-armed brooch, or even a refashioned metal souvenir from the British Isles. Although the garments were of simple design, they were carefully made. In a study of textile fragments from twenty-five women's graves in the west of Norway, Inger-Marie Holm-Olsen found evidence of stitching, hems, sewn-on cord, loops and pleating. The women of Birka,whose clothing has been studied in most detail, were however not representative. As members of a rich trading community with wide international contacts, they did not have to make do with homespun. In fact most of the textiles at Birka appear to have been imported, at least those used for women's clothing and studied in connection with the grave finds. It is also likely that women were buried in their best clothing. They undoubtedly had simpler textiles for everyday wear that are not preserved in burials.
While burials tend to give us information about clothing worn by the higher levels of society, new archaeological techniques can indicate what kind of clothes were worn by poorer people in the Viking Age, often from unexpected sources. Thus, the largest collection of Viking Age textiles comes from the underwater excavation in 1979-80 of the harbour at Haithabu (Hedeby), the southernmost emporium of Viking Age Scandinavia, now in Germany near the Danish border. These textile fragments were all discarded clothing which had been tom up into rags and used in shipbuilding, either for tarring the outside of a ship, or for stuffing into cracks to make it watertight.
The simplest clothes found at Haithabu were made of the roughest woollen fabric, suggesting that these were the clothes of slaves, servants and the poor, or the daily dress of the better-off. The women's garments consisted of very simple ankle-length, long-sleeved dresses, cut loose to enable freedom of movement at work, and possibly a simple wrap or shawl.
Better-quality clothing was also found in the rags of Haithabu and here the finds are similar to those of the clothing from Birka and elsewhere in Scandinavia: over a linen shift, women wore an overdress of fine woollen fabric, held up by the ubiquitous pair of brooches. However, whereas elsewhere the overdress has always been reconstructed as a straight garment, the Haithabu finds indicate that there at least it was tailored at the waist. Tucks and decorative braid running vertically further emphasised the wearer's shape. Outdoors, the better-off women of Haithabu wore an ankle-length coat, again quite wide at the bottom. These coats were made of high-quality dyed wool that had been felled to make it weather-resistant, and were lined, and often quilted with down or feathers for added warmth.
This love of decoration was also noted by Foote and Wilson:
Embroidery was a common occupation; silks, coloured wools and even filaments of precious metal were used. Needles of iron, bone and bronze, sometimes in cylindrical needle-cases, are of quite common occurrence and it has been suggested that the gold and silver thread was inserted with tweezers. To this type of embellishment were added certain simple lace-making techniques. Various embellishments could be added during weaving Tablet-woven strips were used as borders and an interesting technique of manufacturing shaggy cloaks has been found in Viking contexts in the Isle of Man, the Western Isles and Iceland. This pile-weave (ON tong, f., r~oggr, m.) is executed by laying short lengths of wool in the shed or tying them round the warp threads. When woven, the short lengths of wool appear as tufts. The garment produced had the appearance of a shaggy fur. It was an important Icelandic export, but it was also made in Ireland and elsewhere.
However it is unlikely that any Norse female dress was in widespread use on the Island as unlike other parts of the British Isles no characteristic brooch fastening has ever been found.
Very little seems to have recorded about either Irish or Manx costume until the 17th Century.
Blundell , writing in 1648 to disabuse the comment originated by Bishop Merrick (and inserted in Camden's History) that the women went about in their winding sheets states:
First, yt ye women of the Island of Man going abroad they gird themselves about with their winding sheet yt they purpose to be buried in, to shew themselves to be mindful of their mortality.2 I met many so clothed in the Island I confess, and I questioned many of them to know the reason why they did wear them; all answered me that they had no other intention but to keep themselves from the cold and from the bleake and boisterous weather and winds which indeed do much molest them all the winter months.
But Bishop Merrick's relation needs no other eviction than these 3 demonstrations. First, in the Island they are called neither sheets nor shrouds, but are called blankets.
2dly. These blanketts there worn are as well of woolen as of linen cloth (yea ye better sort of them in the country have one blanket for Sundays, another for working days, but all shrouds are of linnen).
3dly. To take away all scruples and foreign conjectures (least it might be thought that these sheets might be in former times intended to make them their shrowds when they died), I will here satisfy you and demonstratively prove that these women never had nor cou'd have at any time any such intention, for I find among other their ancient and accustomed laws yt from all antiquity it hath been there agreed upon for a law yt Sunday blankets shall not be taken for Corbes (yt is it shall not be issued amongst the mortuary goods), but yt it shall go to the next child. By this law it appeareth yt from all antiquity neither the better nor the worser sort of these sheets or blankets (we will not differ upon the name) were at any time used or intended to be used for winding- sheets for the better sort, yt is ye Sunday blankets were to be given to the next child; the worser sort for the week day were taken for corbs, yt is to be sold with the other goods of the deceased to pay debts and to be distributed where legacies were given.
I confidently believe the Manks women took up this custom of wearing blankets from the Irish, their old ancestors and near neighbours, who ever did and do wear mantles for warmth, and not from any relative conceit to make them their winding-sheet; and such a custom also in Wales have the poorer sort of women there to wear in winter men's short cloaks for the same reason, but observe this withal concerning these blankets, that they are only worn and used by the female peasantry of the country inhabitants of the Island of Man, for in the towns you shall not see any one woman (poor or rich) yt do wear any at any time; yet myself being there all the winter season, I did not see so much as any one yt did wear them, so likewise in Wales they are the minor and meaner sort of women that wear men's clokes, the better sort never.
Jeffcott in 1890 discussed some of the Manx words for clothing as a possible clue to the development of costume.
Some description of the costume of common people has been given by various travellers and historians. Lord Teignmouth writing of 1829 states:
The usual dress of the Manks women consists of a jacket and petticoats. They are very proud of, and cherish their long hair. They are also particularly found of showy colours, and wear much the tartan ; this propensity is occasionally severely rebuked from the pulpit. The cheapness and variety of the tartan form its chief recommendation to the Manks, and not its Scotch origin ; this would operate in an opposite manner. The only individual whom I saw in a full suit of tartan, a man of some property, wore it in defiance of the Manks, with whom he had quarrelled. The men are invariably attired in blue coats or sailors jackets, and blue trousers, a complete naval costume. Their shoes worn on week days are made of skins, sometimes covered with hair, fastened with thongs across the foot, called kerranes. I saw them in the mountains. The common brogues of the Highlands of Scotland are of a very superior substance and texture. The children wear no shoes or stockings ; and even adults, when very neatly clad, dispense with them when walking.
That by Train  is probably the most detailed.
Kennish gives a poetical description of Manx Sunday best at the turn of the 19th Century:
While she herself appeard so clean and prim
In her mob-cap of double-borderd rim,
In graceful folds made up by starch and quill
In small round loops by Peggys home-taught skill
Its strings were made of muslin fine and thin,
To form a bow beneath her dimpled chin.
Her quilted silk, of many a diamond shape,
And her short body-dress, with scollopd cape,
She would in homely-modesty display,
She wore the same upon her wedding-day
It graced her mother too Ive heard her say.
The photo published in 1901 corresponds reasonably well to Trains description of 50 years earlier. (another example, also by G.B.Cowen is the Fisherman's Daughter - note these were specially posed shots using his usual models for such work)
See also brief description by C. Roeder.
Judith Jesch in Women in the Viking Age (ISBN
McClintock H.F Old Irish & Highland dress, and that of the Isle of Man Dundalk: Dundalgan Press 1950 2nd (and enlarged ed)
Megaw, B.R.S., and McClintock H.F., The Costume of the Gaelic Peoples Journal Manx Museum Vol V No 71 pp149/160 Dec 1944
Train J., History of the Isle of Man Vol II Douglas:M Quiggin 1842 Chap XVII pp 104/6 covers dress
Manx Woman's Costume Manx Note Book vol ii p187 1887
Manx Girls' Costume in 1800 - J.Manx Mus unpublished doc #223