Mournblade94
Hero
If he doesn't like your backstory, ask him for clarification. If he gives you one, refuse. If you want to name yourself something silly, do it. If he demands that you do things his way or else, take the else and leave. You're right. If he's ruining your fun, he's doing something wrong.
It doesn't sound like the DM is doing anything wrong, it just may not be the style of game your looking for. I have turned players away from my game because of characters they wanted to play, simply because it would not fit with the story. BAsically I gave him options he said no... I said bye. There was thouroughly no loss to me.
Because a player is not having fun in a game does not mean it is the DM's fault. If everyone else is having fun, the group may just not be the proper fit for a player.
If someone wants to play a silly character in my campaign, I tell them the level I can accept. If they insist on playing silly, I tell them to go find another game. Plenty of DM's like silly, I don't. Unless I am playing TOON, or paranoia.
Your animal names would be fine for many groups, but I quite honestly would have problems with them. Its the DM's campaign, and he needs to make sure there is no one that will disrupt the versimilitude.
If your DM is running a good campaign, and you like it, find out how YOU can fit in the story, not how the story can fit around YOU. If the campaign is bad... then who cares, it won't last long.