"the Bishop of Rome as head of the Roman Catholic Church," c. 1200, from Old English papa (9c.), from Church Latin papa "bishop, pope" (in classical Latin, "tutor"), from Greek papas "patriarch, bishop," originally "father" (see papa).
Applied to bishops of Asia Minor and taken as a title by the Bishop of Alexandria c. 250. In the Western Church, applied especially to the Bishop of Rome since the time of Leo the Great (440-461), the first great asserter of its privileges, and claimed exclusively by them from 1073 (usually in English with a capital P-). Popemobile, his car, is from 1979. Pope's nose for "fleshy part of the tail of a bird" is by 1895. Papal, papacy, later acquisitions in English, preserve the original vowel.