Salvete,
Fortuna walks in mysterious ways, the first part of a task we have been given at university consists of making a short vocabulary, based on a text by Lucianos. We can't use our own humble dictionary for this, since it's far from complete, so we have to use the one and only standard work : the Liddel and Scott.
When I'll be working on my part of the text I'll do a quick search for "theoasis", if it's not in there, then it's not an ancient Greek word.
As for "the oasis", great suggestion
if it were a Greek word ending on -is though, it would be pronounced as "theOasis" (a proparoxytonon if you want the proper name
) and not "the oAsis". Of course, the one using this word might have had bad knowledge of ancient Greek accentuation, so that will lead us nowhere
going to rest now after two weeks of fighting against the clock to prepare for various tests, funny thing is, the clock is still ticking.
Valete bene
Lupus