It isn't a real word I'm afraid, but an FBI invention.

https://en.wikipedia.org/wiki/Operation_Onymous

It is a real word though.

http://www.etymonline.com/index.php?allowed_in_frame=0&searc...

Thanks, learned something new.

interesting, I've always used "nonymous" for that, but "onymous" is etymologically sounder

Yeah, I was going to say "nonymous" was etymologically superior, but then I looked up the etymology for anonymous before hitting send.

Given that the English (/Germanic) is "name" and the French is "nom", I would have expected the PIE for name to be some sort of "nVm"-ish thing, whence I expected the Greek to render it is some sort of "non"-ish thing. The actual Greek is ónoma, with the PIE being something like *hnómn. (So my PIE guess was right-ish, but the transition to Hellenic was wrong).

This is Ancient Greek and the antonym is "eponymous". Unfortunately it has a double meaning, used more often as "named after". So we got 'onymous' which has no meaning as an old root.