c. 1300, "shake from fear, cold, etc.," from Old French trembler "tremble, fear" (11c.), from Vulgar Latin *tremulare (source also of Italian tremolare, Spanish temblar), from Latin tremulus "trembling, shaking, quaking," from tremere "to tremble, shiver, quake," from PIE *trem- "to tremble" (source also of Greek tremein "to shiver, tremble, to quake, to fear," Lithuanian tremiu, tremti "to chase away," Old Church Slavonic treso "to shake," Gothic þramstei "grasshopper"). A native word for this was Old English bifian. Related: Trembled; trembling. The noun is recorded from c. 1600.
c. 1600, from French trepidation (15c.) and directly from Latin trepidationem (nominative trepidatio) "agitation, alarm, trembling," noun of action from past-participle stem of trepidare "to tremble, hurry," from trepidus "alarmed, scared," from PIE *trep- (1) "to shake, tremble" (source also of Sanskrit trprah "hasty," Old Church Slavonic trepetati "to tremble"), related to *trem- (see tremble (v.)). Related: Trepidacious (1915).
early 15c., quaveren, "to vibrate, tremble, have a tremulous motion," probably a frequentative of cwavien "to tremble, shake, be afraid" (early 13c.), which probably is related to Low German quabbeln "tremble," and possibly of imitative origin. Meaning "sing in trills or quavers, sing with a tremulous tone" is recorded by 1530s. Related: Quavered; quavering.
late 14c., "causing terror, awe, or dread; frightful," from Old French terrible (12c.), from Latin terribilis "frightful," from terrere "fill with fear," from PIE root *tros- "to make afraid" (source also of Sanskrit trasanti "to tremble, be afraid," Avestan tarshta "scared, afraid," Greek treëin "to tremble, be afraid," Lithuanian trišėti "to tremble, shiver," Old Church Slavonic treso "I shake," Middle Irish tarrach "timid"). Weakened sense of "very bad, awful" is first attested 1590s.