Source : Webster's Revised Unabridged Dictionary (1913)

Trigger \Trig"ger\, n. [For older tricker, from D. trekker, fr.
   trekken to draw, pull. See {Trick}, n.]
   1. A catch to hold the wheel of a carriage on a declivity.

   2. (Mech.) A piece, as a lever, which is connected with a
      catch or detent as a means of releasing it; especially
      (Firearms), the part of a lock which is moved by the
      finger to release the cock and discharge the piece.

   {Trigger fish} (Zo["o]l.), a large plectognath fish
      ({Balistes Carolinensis} or {B. capriscus}) common on the
      southern coast of the United States, and valued as a food
      fish in some localities. Its rough skin is used for
      scouring and polishing in the place of sandpaper. Called
      also {leather jacket}, and {turbot}.