It's been stated in one of the interviews but I don't remember where (I think it was some 5 page one that one of the members here did) that it is Ozzy, and that he pronounced the name differently on purpose.
I remember reading the interview Octillus is talking about, as Biert says it's probably the French equivalent of John Michael, but it's probably a bit tricky for an English speaker to say "Jean" blandly without pronouncing the "n" a bit (and it would sound ugly in the middle of an English song, I'm not sure how French is perceived for non-French people, but as one, I really find it difficult to make sound good for singing).
Thoughts inspired by devil, posture inspired by angle :/