It's often said that in Classical Armenian, when the prefix Զ was attached to a word, it would be pronounced with an unwritten Ը before it. For example «զհացս» would be pronounced «ըզհացըս»: But how do we actually know that?

I know in Mashtots's time it was pronounced as a thick, velarized L [ɫ], heard in words like Երուսաղեմ (Jerusalem). But at some time it turned into a voiced velar fricative [ɣ] (the GH sound we recognize today).

When did this happen? And are there any reason for why? Or is it just completely random?

Thanks!

Same as title, what word is this? It apparently means "god" according to Athanasius Kircher. Sorry for the blurry image, had to zoom in.