masc. proper name, from L.L. Hilarius, lit. "cheerful," from L. hilaris (see hilarity). The name was more popular in France than in England. The woman's name (M.E. Hillaria) seems to be merged from Eulalia, name of the patron saint of Barcelona, a Latinization of Gk. eulalos
"sweetly speaking." The Hilary sessions of British High Court and universities (1577) are from St. Hilarius, Bishop of Poitiers, obit. C.E. 368, whose feast day is Jan. 13.