When white smoke rises from the Sistine Chapel signifying a man has been elected to the papacy, he chooses a papal name and is bestowed with eight official titles. It might surprise you that of those eight titles, pope is not one of them. So then, why do we call the pope “the pope?”
In the very early years of the Church, the terms “episcopos” and “presbyter” were used interchangeably to refer to local congregations lead by bishops. The first usage of the word páppas, pope in Greek meaning “father”, to refer to a church leader was in regard to the Patriarch of Alexandria, Pope Heraclas of Alexandria. In a letter written by his successor, Pope Dionysus of Alexendria (reigned 248 A.D. to 264 A.D to Philemon, a Roman presbyter he makes mention of a “Pope Heraclas.”
“τοῦτον ἐγὼ τὸν κανόνα καὶ τὸν τύπον παρὰ τοῦ μακαρίου πάπα ἡμῶν Ἡρακλᾶ παρέλαβον.”
“I received this rule and ordinance from our blessed father/pope, Heraclas.”
In the East, the honorific designation of “pope” was reserved for the Bishop of Alexandria. However, in the West it was used for any bishop. The earliest extant record of the word papa being used in reference specifically to the Bishop of Rome dates to late 3rd century, when it was applied to Pope Marcinellus.
The first usage of the English word “pope” arrives the year 950 A.D., in an Old English translation of Bede’s Ecclesiastical History of the English People making reference to Pope Vitalian.
“Þa wæs in þa tid Uitalius papa þæs apostolican seðles aldorbiscop.
In Modern English:
At that time, Pope Vitalian was chief bishop of the apostolic see.”
Today, the pope title continues to refer to the Alexandrian bishops, both Coptic Orthodox and Greek Orthodox Patriarchs of Alexandria are known as the “Pope and Patriarch of Alexandria.”
In the West, the pope title became reserved chiefly for the Bishop of Rome around the 5th and 6th centuries. In 998, an Archbishop of Milan was rebuked for having called himself pope. In 1073, Pope Gregory VII issued a decree that no other bishop of the Catholic Church could hold the title except the Bishop of Rome.