Trepidation \trep-uh-DAY-shuhn\ , noun;
1. [archaic] An involuntary trembling; quaking; quivering
2. A state of dread or alarm; nervous agitation; apprehension; fright
According to Etymonline.com:
The word dates to around 1600 and comes from Latin trepidationem (nominative: trepidatio), meaning "agitation, alarm, trembling." It is a 'noun of action' from the past participle stem of trepidare ("to tremble, hurry") from trepidus ("alarmed, scared"). The Latin word derives from Proto-Indo-European *trep-, meaning "to shake, tremble." *Trep- also lead to Sanskrit trprah ("hasty"), and Old Church Slavonic (the great-grandparent of all Slavic tongues) trepetati ("to tremble").
*Today's word and the first definition were both taken from Dictionary.com's 'Word of the Day' for Friday, October 29