masc. proper name, from Late Latin Hilarius, literally "cheerful," from Latin hilaris "cheerful" (see hilarity). The name was more popular in France than in England. The woman's name (Middle English Hillaria) seems to be this name merged with Eulalia, name of the patron saint of Barcelona, whose name is a Latinization of Greek eulalos "sweetly speaking." The Hilary sessions of British High Court and universities (1577) are from St. Hilarius, Bishop of Poitiers, obit. C.E. 368, eminent Church father and opponent of the Arians, whose feast day is Jan. 13, the Octave of the Epiphany.