The Collaborative International Dictionary of English v.0.48:

Mummichog \Mum"mi*chog\, n. [Amer. Indian name.] (Zool.)
   Any one of several species of small American cyprinodont
   fishes of the genus Fundulus, and of allied genera; the
   killifishes; -- called also minnow. [Written also
   mummychog, mummachog.]
   [1913 Webster]