Trigger

trigger
1. A catch to hold the wheel of a carriage on a declivity.
2., the part of a lock which is moved by the finger to release the cock and discharge the piece.
(Science: zoology) Trigger fish, 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.
Synonym: leather jacket, and turbot.
Origin: For older tricker, from D. Trekker, fr. Trekken to draw, pull. See Trick.