Old English papa (9c.), from Church Latin papa "bishop, pope" (in classical Latin, "tutor"), from Greek papas "patriarch, bishop," originally "father." Applied to bishops of Asia Minor and taken as a title by the Bishop of Alexandria c.250. In Western Church, applied especially to the Bishop of Rome since the time of Leo the Great (440-461) and claimed exclusively by them from 1073 (usually in English with a capital P-). Popemobile, his car, is from 1979. Papal, papacy, later acquisitions in English, preserve the original vowel.
The head of the Roman Catholic Church. The pope is believed by his church to be the successor to the Apostle Peter. He is bishop of Rome and lives in a tiny nation within Rome called the Vatican. Catholics believe that when the pope speaks officially on matters of faith and morals, he speaks infallibly (see papal infallibility). (See also John XXIII and John Paul II.)