There's this hit for
Yvain (which is male):
http://www.behindthename.com/name/yvain
It seems to me that a lot of authors made up pseudo-Celtic or pseudo-Gaelic names to suit their purposes. There's user-submitted info for Yvaine that links it to the name
Gavin (they share a root, according to this person) but in my opinion, Yvaine is most likely either a derivative of
Yvain or a pseudo-Welsh name derived from a known name like Ygrainn (notice the similarity?).
Perhaps someone else will come along who knows better, but it is my educated guess that Yvaine was formed from known Welsh elements to suit Gaiman's purposes.
*edit: The DB only recognizes
Igraine, but I know I have seen Ygrainne and Ygrainn as well. Hopefully someone else pokes along who can correct me and/or add more info.*
This message was edited 6/25/2008, 9:22 PM