The name Hilary derives from the Latin name Hilarius, which means "cheerful" or "merry." The name gained popularity during the early Christian era, and its origins can be traced back to ancient Rome.

In the 4th century, St. Hilary of Poitiers (c. 310-367), a renowned Bishop and Doctor of the Church, helped spread the name throughout the Christian world. His influential writings and theological works made him a significant figure in the history of the Catholic Church.

During the Middle Ages, the name Hilary was relatively common, particularly in England and France. One notable figure from this period was Hilary of Arles (c. 401-449), a French bishop and saint known for his efforts in promoting monasticism.

In the 12th century, Hilary of Chichester (c. 1109-1169), an English saint and Bishop of Chichester, was venerated for his piety and charitable works. His cult following helped further popularize the name in England.

In the Renaissance period, the name Hilary gained renewed interest. One prominent figure was Hilary Term (c. 1466-1535), an English jurist and lawyer who served as the Lord Chancellor of England under King Henry VIII.

During the 17th century, Hilary Prideaux (1648-1724) was an English churchman and scholar who made significant contributions to biblical studies and wrote a influential work titled "The Old and New Testament Connected in the History of the Jews and Neighbouring Nations."

Throughout history, the name Hilary has been borne by various notable individuals, including Hilary Mantel (1952-2023), a British writer and two-time winner of the Booker Prize; Hilary Clinton (born 1947), an American politician and former First Lady; Hilary Swank (born 1974), an American actress and two-time Academy Award winner; Hilary Duff (born 1987), an American actress and singer; and Hilary Hahn (born 1979), an American violinist and Grammy Award winner.