The Collaborative International Dictionary of English v.0.48:

Trapper \Trap"per\, n. [From Trap to insnare.]
   1. One who traps animals; one who makes a business of
      trapping animals for their furs. --W. Irving.
      [1913 Webster]

   2. (Mining) A boy who opens and shuts a trapdoor in a gallery
      or level. --Raymond.
      [1913 Webster]

WordNet (r) 3.0 (2006):

trapper
    n 1: someone who sets traps for animals (usually to obtain their
         furs)