Just don't copy other tribe names, I can't stand people who do that.
Oh, and don't do something really generic like "Knights of Chaos" or "United Nations" or "Kings of Hell" or "Hellish Knights" or "Demonic Knights" or (you get the picture).
The point of a tribe name, I'd think, would be to represent what your tribe would be. Historically, there were a great number of strong warriors, and spokespeople. Find something in history, that matches what you want for your tribe