Well, let's see. "Fire", as in "pretty flame". I have some slightly pyro tendancies when the mood takes me. (Not usually, just occaisionally). And "foot" as in 12 inches. So I'm a 12 inch flame.
Seriously, though, Firefoot is the name of Éomer's horse and I have no idea why I picked that at the moment. It just sounded cool, I guess.