The Collaborative International Dictionary of English v.0.48:
Doge \Doge\, n. [It doge, dogio, for duce, duca, fr. L. dux, ducis, a leader, commander. See Duke.] The chief magistrate in the republics of Venice and Genoa. [1913 Webster]WordNet (r) 3.0 (2006):
doge n 1: formerly the chief magistrate in the republics of Venice and Genoa