“surnom” is indeed a correct translation of nickname in its classical use, but it’s not used on the internet. If you happen to say, lack hair, maybe your friends will give you the “surnom” “baldy”, but “mangeorge” is your “pseudo”.
Thanks, DarrenS!
Nom de theatre: 183 Google Hits (162 in English Only Search)
Nom de scene: 1,070 Google Hits (93 in English Only Search)
Nom des planches: 11 Google Hits (no hits in English Only Search)
Nom d’artiste: 309,00 Google Hits (7,020 English Only Search)
If we can get a ruling on this from clairobscur on this, that would be awesome.
clairobscur, thanks for the clarification.
BTW; Are you native French? An expat? I ask because your English (here, at least) is nearly perfect. Also, did you guys really steal the original french fries from the Belgians? 
Regardless where they were first created, the American term “French fries” is actually a corruption of “frenched fries” referring to the method of slicing the potatoes into thin strips. (Frenching (as a verb to slice vegetables into thin strips) appears to have fallen out of general use in the States, replaced by the adjective julienne.)
owlstretchingtime, please note that a general slur such as “cockpockets” is not appropriate to GQ.
[ /Moderator Mode ]
** DarrenS ** was perfectly correct.
And “nom de scene” would be the most proper term in french for the made up name assumed by an actor. “Nom d’artiste” can be used to, though, but the reason why you got so many hits is that it means “artist name” or “name of artist”, so you can find it in many sentences, like, say, “search by artist name”. “Planche” means “plank”, so your hits probably have nothing to do with theater, though “les planches” (the wood floor you’re standing on when acting) is indeed used to refer metaphorically to the stage.
And by the way, thanks for the compliment. I’m a native french speaker. Also, you were right to add “at least here”. My ability to speak english, or to understand spoken english is sorely limited.
Oh! And french fries are definitely Belgian. The caricatural Belgian refered to in the very common Belgian jokes (“How do you notice there’s a Belgian aboard a submarine? He’s the one wearing a chute”, “Belgian helicopter crashes in a cemetary. Authorities announce they recovered the bodies of 863 victims”, and so on…) always eat fries.