I've always liked the sound of nabob (or nawab): < Hindi nawāb, nabāb < Arabic nuwāwb (pl. of nā’ib 'deputy' active participle of nāba 'to represent'. And, of course, negus is pretty cool, too: < Amharic nəgus < Classical Ethiopic nəgu 'king, ruler' verbal adjective of nagśa 'to rule, become king'.