who'd a thought betray would be related?

Yes, betray is from betrayen from OFr trair from tradere from trans- plus dare. Dora as in the names Doris and Theodore. Does everybody know that Pokorny is online? Sort of. Plus a whole bunch of other great dictionaries, like Vasmer. Fantastic resource for etymologists of every stripe.

http://iiasnt.leidenuniv.nl/ied/