An Etymological Dictionary of Astronomy and Astrophysics

1a) (n.) Anything, as an act or event, that serves as a stimulus and initiates or precipitates a reaction or series of reactions.
1b) In electronics, the signal or stimulus that initiates a → trigger circuit.
2) (v.) To initiate or precipitate (a chain of events, scientific reaction, psychological process, etc.).

Etymology (EN): Earlier tricker, from Du. trekker “trigger,” from trekken “to pull,” from M.Du. trecken (cf. M.L.G. trecken, O.H.G. trechan “to draw”).

Etymology (PE): 1) Mâšé “a trigger, tongs, pincers,” of unknown origin.

2. Mâšidan, infinitive from mâšé, as above.