Why not a combination of those suggestions? Link what name is used to who is using it, and under what circumstances. So, when they're talking about themselves or an outsider is being nice, they use either Magari if they're talking about current residents or Mācēhualli if they're talking about people of a more tribal descent. Sort of a distinction between the dwarven kingdoms and the aboriginals that you know are running around in there. IN addition, those attached to a particular kingdom will probably use that kingdom's name as well.
Outsiders can call them Bonites if they're being more vulgar in speech, and either Boneheads or even Boners if they're being derogatory. Heck, let boner mean the same think in L4W it does on Earth, and you've just invented a new way to call someone a wanker and tied it into the setting proper!