exhilarate v.

word-forming element, in English meaning usually "out of, from," but also "upwards, completely, deprive of, without," and "former;" from Latin ex "out of, from within; from which time, since; according to; in regard to," from PIE *eghs "out" (source also of Gaulish ex-, Old Irish ess-, Old Church Slavonic izu, Russian iz). In some cases also from Greek cognate ex, ek. PIE *eghs had comparative form *eks-tero and superlative *eks-t(e)r-emo-. Often reduced to e- before -b-, -d-, -g-, consonantal -i-, -l-, -m-, -n-, -v- (as in elude, emerge, evaporate, etc.).

mid-15c., from Latin hilaritatem (nominative hilaritas) "cheerfulness, gaiety, merriment," from hilaris "cheerful, merry," from Greek hilaros "cheerful, merry, joyous," related to hilaos "graceful, kindly," hilaskomai "to propitiate, appease, reconcile,"and probably from a suffixed form of a PIE root *selh- "reconcile" (source also of Latin solari "to comfort").

In ancient Rome, Hilaria (neuter plural of hilaris) were a of holidays, times of pomp and rejoicing; there were public ones in honor of Cybele at the spring equinoxes as well as private ones on the day of a marriage or a son's birth.