The following are the early names of the Island as given by various historians :
B. C. 54 Caesar Mona.
A. D. 23 Pliny Monapia.
A. D. 139 Ptolemy Monada.
A. D. 416 Orosius Mevania.
A. D. 858 Nennius Eubonia.
A. D. 1084-1496 Irish Annals Manann, Manand.
A. D. 1154 Welsh Annals Manaw.
A. D. 1240 Scand. Sagas Mon, Maon.
All succeeding historians copy one or other of these forms, occasionally slightly modified. Orosius form seems to be a metathesis of Plinys, i.e. Mevanja for Menavia. Nennius form is a litlle Puzzling ; the Annals of Wahes, c. 125 give Eumonia, whichi seems more correct. In any case, as the form is a comparatively late one, it need not be discussed here. Neniijus may have miscopied the name, for he appears to be in doubt as to its correctness. He says 'et vocatur nomen ejus Eubonia, id est Mana (and called by its name Eubonia, that is Manau). The latter is the Welsh name, with which Nerinius seemed to he more familiar than with Eubonia. The forms in the Irish Annals are usually genitive, thus in the Annals of Tighernach C. A. D. 1084 we find cath Manand, battle of Mann. The early stem of the name was mon or mona as evidenced by the three earliest historians, and the various terminations added by later wiiters were either locative or simply indicated case. In Caesars time Mona must have been sounded [m3na] with short medial vowel, and not [mo:na] , with long vowel, as it is now pronounced. In Irish it was written Mana, which had approximately the same sound as Caesars Mona.
The late Prof. Rhys (in Manx Names) suggests that the pre-historic form was Manavjo, genitive Manavjonos, which might account for Plinys form ending in -pia. But ifsuch a form ever existed, one would expect to find a trace of it in Caesars. Many of the Old Irish case-endings are found on the Ogham monuments as late as the fifth century. It is almost certain that Caesar set down the name as he heard it, and that later writers, subsequent to Pliny, copied the latters form with various modifications.
The Old Irish form would be Mana or Mann, genitive Manann, dative Manainn, hence the modern Manx name Mannin is the old dative. The Scandinavian Mon had a genitive Manar. The later Latin name was Mannia with a genitive Manniæ.
There has been much speculation in regard to the meaning of the name, and many derivations have been suggested, some of them of a wild and imaginative character. The late Dr. McBain, in dealing with Ptolemys geography of Scotland, traced most of the names to Celtic roots, but mainly belonging to the Brythonic rather than to the Goidelic branch, thus proving that the Pictsthe ancient inhabitants of Scotlandwere closer akin to the Welsh than to the Gael.
Our three earliest forms of the name by Caesar, Pliny and Ptolemy, contain the root moit, which may be equated with Gaelic moncrdh, Welsh mynydd, and also Latin mons, mountain. This is the usual Gaelic name for mountain ; slictbh, which is so common in Ireland and Man, with the same meaning, being usually applied to a moor in Scotland. Monadh is therefore Pictish rather than Gaelic, and indicates that the Isle of Man was in early times, like Scotland. inhabited by a tribe of Picts. There were also Pictish tribes in Ireland, and Galloway was peopled by the same race within historic times.
The name Mona or Mana therefore means mountainous or hilly land, and was also the early name of Anglesey
It has been surmised by some that the Island took its name from a tribe called the Menepii, who inhabited a tract of land on the east coast of Ireland in Ptolemys time. This tribal name meant hill-men, but whether they had any connection with Man it is impossible to say The late Prof. Rhys suggested that Mann may have taken its name from Manannán, the Celtic Neptune, but it is much more probable that Manannán took his name from the Island. The suffix nán, conveyed the idea of littleness, which sometimes included endearment ; thus Manannán means little Manxman, and in Manx tradition he is called Manannan beg mac y lir, little Manannan son of the sea, showing that the idea of diminutiveness was associated with him.
In Irish tradition one of the names of the Island was mis Falger, which is probably synonymous with mis Ealga, an old poetic name of Ireland, meaning Isle of nobility.
see also 'Name Man'