The Collaborative International Dictionary of English v.0.48:

Impoon \Im*poon"\, n. (Zool.)
   The duykerbok.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Duykerbok \Duy"ker*bok\, n. [D. duiker diver + bok a buck, lit.,
   diver buck. So named from its habit of diving suddenly into
   the bush.] (Zool.)
   A small South African antelope (Cephalous mergens); --
   called also impoon, and deloo.
   [1913 Webster]