This may be a little bit off the core subject area, but I have a reference in a journal from the 1790s to a place called "Ysayos Tavern", which made no sense to me. 

I have a reference in the same general geography to a man "Isaac" who had a tavern.

Since I would pronounce "Isaac" as "I-sack", I could not make a connection.

Recently I heard someone pronounce an organization name which started with "Isaac" as "I-say-alk" and suddenly the phonetic 18th century "Ysayos" seemed not so far off.

Does anyone have any insights on whether "Isaac" would be pronounced in this manner in the late 18th century - or any other time for that matter?