Word Origin & History
hilarity
1440, from L. hilaritas (gen. hilaritatis) "cheerfulness, gaiety," from hilaris "cheerful, gay," from Gk. hilaros, related to hilaos "graceful, kindly." In ancient Rome, Hilaria (neut. pl. of hilaris) were a class 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.