Do you know ghouls from goblins and ghosts?
1650s, earlier tricker (1620s), from Dutch trekker "trigger," from trekken "to pull" (see trek). Tricker was the usual form in English until c.1750. Trigger-happy is attested from 1943.
1930, from trigger (n.). Related: Triggered; triggering.
Quick to respond or react; touchy; sensitive (1940s+)
A gunman; hit man, trigger man: He's a trigger (1935+ Underworld)
quick on the draw