In Latin, literally the ‘greatest bridge-maker’ was the high priest of the Collegium Pontificum, the ‘College of Pontiffs’ in ancient Rome.
This was the most important position in the ancient Roman religion, open only to patricians until 254 BC, when a plebeian first occupied this post. A distinctly religious office under the early Roman Republic, it gradually became politicized until, beginning with Augustus, it was subsumed into the Imperial office. Its last use with reference to the emperors is in inscriptions of Gratian who reigned between 375–383. He, however, decided to omit the words pontifex maximus from his imperial title.
The word pontifex later became a term used for Christian bishops, including the Bishop of Rome, and the title of Pontifex Maximus was applied within the Roman Catholic Church to the Pope as its chief bishop. It is not included in the Pope’s official titles, but appears on buildings, monuments and coins of popes of Renaissance and modern times.
The title of Pontifex Maximus, which is now applied to the pope, though not included in his official list of titles, thus has a very ancient history, dating back to the times of the Roman Republic. The only title applied to the Pope that has a longer documented history is the word pope itself, which is found already in the time of Homer. This title likewise is not included in the official list of his titles, but is used in official documents – such as the headings of encyclicals and similar documents – far more commonly than the title Pontifex Maximus, which is in practice used in little more than inscriptions of buildings.