also anti-pope, early 15c. (mid-13c. in Anglo-Latin), from Medieval Latin antipapa, from Greek anti "against, opposite, instead of" (see anti-) + papa (see pope). There have been about 30 of them, the last was Felix V, elected at Basel in 1439.
word-forming element of Greek origin meaning "against, opposed to, opposite of, instead," shortened to ant- before vowels and -h-, from Old French anti- and directly from Latin anti-, from Greek anti (prep.) "over, against, opposite; instead, in the place of; as good as; at the price of; for the sake of; compared with; in opposition to; in return; counter-," from PIE *anti "against," also "in front of, before" (from root *ant- "front, forehead," with derivatives meaning "in front of, before"), which became anti- in Italian (hence antipasto) and French.
It is cognate with Sanskrit anti "over, against," and Old English and- (the first element in answer). A common compounding element in Greek, in some combinations it became anth- for euphonic reasons. It appears in some words in Middle English but was not commonly used in English word formations until modern times. In a few English words (anticipate, antique) it represents Latin ante.
In noun compounds where it has the sense of "opposed to, opposite" (Antichrist, anti-communist) the accent remains on the anti-; in adjectives where it retains its old prepositional sense "against, opposed to," the accent remains on the other element (anti-Christian, anti-slavery).
"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.
<a href="https://www.etymonline.com/word/antipope">Etymology of antipope by etymonline</a>
Harper, D. (n.d.). Etymology of antipope. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/antipope