>I just about the vocal harmony in Hungarian. Can it be the "e" is the
>one which triggered the change? *uweg > *euweg > üveg?
In Hungarian, stressed syllables consisting of (<vowel>v) are common
occurrences and very stable (öv, ivadék, üvölt, avatkozik, evett, ivott,
óvoda, év &c.)
As for the harmony, I'd say eveg, éveg, iveg, öveg, üveg would fit.
To a lesser extent aveg (if haver and krapek fit, then aveg, too;
but I underline: from today's point of view); áveg even lesser or no.
I'd tend to change e /ae/ > a /O/ in these cases: avag, ovag, óvag,
uvag, úvag. (Cf. kavar, anyag, agyag, lovag, udvar.) Ö, ü could also
give övög, üvög (but no: övüg, üvüg).
George