Outlines of Gaelic etymology.
xi.
i becomes ea: fear from *viro‑s.
éi becomes ia: the stem féidh becomes fiadh in the nom. (*veido‑s).
ì becomes ìo: fìor from *vîro‑s.
Mutation by “u.”
A succeeding u affects only i or e; it is a mutation which does not now operate. Thus fiodh comes from *vidu- (O. Ir. fid); bior from *beru (O. Ir. bir); sliochd from slektu‑; cionn from the dat. *cennū, from *cennō.
§ 3. Indo-European and Gaelic Vowels.
The representation in Gaelic of the I. E. vowels is very complicated owing to the principles of mutation discussed above.
I. E. i.
(1) Gaelic i, O. Ir. i, W. y.
- bith, world, O. Ir. bith, W. byd, Br. bed: *bitu‑s, root ꬶi. So ith, fidir, nigh, fir (gen. and pl. of fear), as also nid from nead, etc.).
(2) G. ea, O. Ir. e.
- beatha, life, O. Ir. bethu: *bitûs, stem *bitât‑, root ꬶi. So eadh, it, fear, geamhradh, meanbh, nead, seas, seasg, sleamhuinn, sneachd.
(3) G. io, O. Ir. i.
- G. fiodh, wood, O. Ir. fid, W. gwydd, Br. gwez: *vidu‑. So fios, iodh‑. The io of fionn, O. Ir. find is due to the liquid and medial mute, which together always preserve the i and even develop it from an original ṇ or en (ṇb, ṇd, ṇg).
(4) G., O. Ir. iu.
- This is a mutation by u: fliuch, wet, from *vliqu‑; tiugh, *tigu‑s.
I. E. u.
(1) G., O. Ir. u, W. w (o).
- G., O. Ir. sruth, stream, W. frwd: *srutu‑s. So bun, dubh, guth, muc, musach, slug, smug, tulach.
- Here add G. ui: cluinn, luibh, uisge.
(2) G., O. Ir. o.
- bonn, bottom, O. Ir. bond, W. bon, *bundo‑s. So bothan, con, dogs’, do‑, so‑, domhan, dorus, tom, os, trod.
I. E. e.
(1) G., O. Ir. e, W. e.
- Simple e is rare in G.: leth, side, O. Ir. leth, W. lled, *letos. So teth, hot.
