hilarymas

\\ˈhil(ə)rēməs\ noun (-es)

Usage: usually capitalized

Etymology: Middle English Hillarimesse, from St. Hilary died ab A.D. 367 bishop of Poitiers + Middle English messe mass — more at mass

: the feast of St. Hilary on January 13 in the Anglican calendar and January 14 in the Roman Catholic calendar