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c.1600, 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- "to shake, tremble" (cf. Sanskrit trprah "hasty," Old Church Slavonic trepetati "to tremble"), related to *trem- (see tremble).
trepidation trep·i·da·tion (trěp'ĭ-dā'shən)
An involuntary trembling or quivering.
A state of anxious fear; apprehension.