Thanks for the reply.
I hope you understand that I don't mean that any name that sounds like a Greek name, it has actually came from Greek. I would be at least silly if I do that! All I want to do is think and search and ask people's opinion about different options on the etymology. Thats why I started my first post as: "Could ADA
not be a short for ADELAIDE
?" and not as: "ADA
is a short for ADELAIDE
Anyway, thats what is all about, find the truth through dialogue, sensible thinking and research, isnt it? :0)