The Collaborative International Dictionary of English v.0.48:

Wombat \Wom"bat\, n. [From the native name, womback, wombach, in
   Australia.] (Zool.)
   Any one of three species of Australian burrowing marsupials
   of the genus Phascolomys, especially the common species
   (Phascolomys ursinus). They are nocturnal in their habits,
   and feed mostly on roots.
   [1913 Webster]