BULGAR

That's a puzzle. The name of the city and people on the Volga, which eventually took part in the etymology of "Bulgaria", definitely contains the Svan plural "-ar" suffix. The root "bulg-" is not visible in Kartvelian dictionaries. But there is no doubt that it is identical to the word "Volga", on which, in fact, Bulgar was located.

The word "volga" indeed shows two Megrelian morphemes. One of them is the negative "vo-" prefix. Meanwhile the "lg" root is present in the Russian toponym "Lgov". The toponym is definitely Megrelian for it ends with the Megrelian genitive "-ou" suffix. Should be some lost "lga" word (ლგა/ლღა), which is also present in "Volga". The whole hypothesis is supported more by the undoubted Megrelian origin of the Bulgars/Bolgarians.

So, still a mystery.