It is interesting that John McCaskell seems to have acquired his holding in Gren[a]by Treen, Bride, since the oldest c1490 roll, as there is no sign of him or his name there. In fact the names and rents are quite mixed up compared to 1513.
Another mystery is that the McCash family disappear from the rolls in the same period, but in another part of the parish. Apparently Ballakesh derives from McCash not Kewish as per GB and the Radcliffes. I cannot see how McCash could become McCaskell all that easily, so therefore just a coincidence.
Unfortunately the treen of Crosby Beg is missing c1490 and defective 1513 + CKR wrote that the QL's of Kerrow ny Traie and Kionlough always belonged together. However we cannot check because of damage etc so the McCaskell's might be there already in 1490's.