Meaning and history
Hilarius is a Latin name derived from hilaris, meaning “cheerful,” though it may also come from the Greek name Ἱλαρός (Hilaros), with the same meaning, since the Greek word ἱλαρός was the source of the Latin term. Notable bearers include Saint Hilarius, a 4th-century theologian and bishop of Poitiers, and a 5th-century pope of the same name.