fore a or o, whilst o changes to u before
i, u, cf. Ir. _muir_, "sea," Prim. Celt. _*mori_, gen. sing. _mora_. Of
Brythonic finals which disappear, a, i, (o), j alone influence preceding
vowels, whilst an i (y) which received the stress in O. W. was also able
to modify vowels which went before it. In Goidelic the combinations
_sqv_, sv appear respectively as sc, s (medially, f), but in Brythonic
they both give _chw_; Prim. Celt. _*sqvetlon_, Ir. _scel_, "story," W.
_chwedl_; Prim. Celt. _*svesor_, Ir. _siur_, "sister," but _mo fiur_,
"my sister" (whence Scottish _piuthar_ by false de-aspiration), W.
_chwaer_, Bret. _c'hoar_. In Brythonic initial s becomes h in the 7th
century, but this is unknown in Goidelic, e.g. Ir. _salann_, "salt," W.
_halen_, Cornish _haloin_, Bret, _holenn_; Lat. _se-men_, Ir. _sil_,
"seed," W. _hil_. Initial v gives f in Goidelic in the course of the 7th
century, whereas in Brythonic it appears as _gu, gw_, cf. Lat. _verus_,
Ir. _fir_, W., Bret. _gwir_. We may also mention that in Goidelic
initial j and medial v disappear, e.g. Gaulish _Jovincillus_, W.
_ieuanc_, "young," Bret, _iouank_, Ir. _oac, oc_; W. _bywyd_, "food,"
Ir. _biad_. Post-consonantic j in Brythonic sometimes gives -id (Mod. W.
_-ydd_, Mod. Bret, -ez), e.g. Gaulish _nevio-, novio-_, O. Bret,
_nowid_, W. _newydd_, Bret, _nevez_, Ir. _nue._ I.E. -kt and -pt both
appear in Goidelic as _-cht_ but in Brythonic as _-ith_, cf. Lat.
_septem_, O. Ir. _secht_, W. _seith_, Bret. _seiz_.

We unfortunately know very little about the position of the stress in
ancient Gaulish. According to Meyer-Lubke in place-names the penult was
accented if the vowel was long, otherwise the stress lay on the
preceding syllable, e.g. _Augustodunum_, O. Fr. _Ostedun_, now _Autun;
Catalaunos_ (Chalons), _Tricasses_ (Fr. Troyes), _Bituriges_ (Fr.
Bourges). In Goidelic the stress, which is strongly expiratory, is
always placed on the first syllable except in certain cases in verbs
compounded with prepositional prefixes. In Old Welsh and Old Breton, on
the other hand, the final syllable, i.e. the primitive penult, received
the stress, but in both languages the stress was shifted in the middle
period to the penultimate. The Goidelic dialects, like the Slavonic,
distinguish between palatalized and nonpalatalized consonants, according
as the consonant was originally followed by a front (e, i) or back vowel
(a, o, u), a phenomenon which is entirely unknown to Brythonic.