trigger (n.) Look up trigger at Dictionary.com
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.
trigger (v.) Look up trigger at Dictionary.com
1930, from trigger (n.). Related: Triggered; triggering.