>Incidentally, Greek has also this kind of reinforcement *y- > z-, which has also been explained as the result of the same mechanism. However, I can't accept it because the coverword "laryngeal" doesn't describe a definite type of consonant in modern *scientific* standards.
> > IMHO the French word would rather reflect Celtic (Gaulish) *kladiwo-
> > (not **kladio-). However, the Italoid (aka Sorothaptic) protoform
> > *k(a)lawijo- proposed by Coromines could explain the Celtic word through
> > metathesis and reinforcement of yod (like in East Germanic): *klawijo- >
> > *klajiwo- > *kladiwo-.
> The Verscharfung observed in Crimean Gothic <ada> 'egg' and the like has been explained by Lehmann as resulting from a laryngeal clustered with the yod, and I know of no other satisfactory mechanism.
> Rather than two ad-hoc assumptions,All things being equal, the "laryngeal" hypothesis is also what you call an "ad-hoc assumption".