detonador
/detonaˈdoɾ/ · B2 · adj
trigger, cause
💣 detona- (detonate) + -dor (-er) = the one that makes it go boom
Detonador splits into detonar (to explode, from Latin detonare, to thunder down) plus the agent suffix -dor, meaning one that does. So it is the thing that sets off an explosion, and by extension any trigger or cause that sets off other events.