Popes change their names as a longstanding tradition that symbolizes their new role and mission as the leader of the Roman Catholic Church. This practice began in 533 AD when Pope John II changed his birth name Mercurius, which was associated with a pagan god, to a Christian name. The new papal name often reflects homage to previous popes or saints whom the new pope admires or wishes to emulate, and it can symbolically define the direction or emphasis of their papacy. Although not a doctrinal requirement, adopting a new name has become an integral tradition over centuries, representing a form of "second birth" upon becoming pope. The tradition solidified around the 10th century and has been followed by nearly all popes since, with very few exceptions in history who retained their birth names.
