Zosimus, New History 4.36
Zosimus (Greek Ζώσιμος): Early Byzantine, pagan author of a history of the Roman Empire, published in the first quarter of the sixth century CE.
The translation of Zosimus' New History offered here was printed in 1814 by W. Green and T. Chaplin in London, and was probably prepared by J. Davis of the Military Chronicle and Military Classics Office. The translator is anonymous. The text was found at Tertullian.org. The notes were added by Jona Lendering.
[4.36.1] Upon this occasion it may not be improper to relate a circumstance which has some reference to the present part of my narration. Among the Romans, the persons who had the superintendence of sacred things were the pontifices, whom we may term gephyraei if we translate the Latin word pontifices (which signifies bridge-makers) into the Greek.note[The etymology is false; the word is in fact Etruscan.] The origin of that appellation was this: at a period before mankind were acquainted with the mode of worshipping by statues, some images of the gods were first made in Thessaly.
[4.36.2] As there were not then any temples (for the use of them was likewise then unknown), they fixed up those figures of the gods on a bridge over the river Peneus, and called those who sacrificed to the gods, gephyraei, Priests of the Bridge, from the place where the images were first erected. Hence the Romans, deriving it from the Greeks, called their own priests pontifices, and enacted a law that kings, for the sake of dignity, should be considered of the number.
[4.36.3] The first of their kings who enjoyed this dignity was Numa Pompilius. After him it was conferred not only upon the kings but upon Octavian and his successors in the Roman empire. Upon the elevation of any one to the imperial dignity, the pontifices brought him the priestly habit, and he was immediately styled, Pontifex Maximus, or chief priest.
[4.36.4] All former emperors, indeed, appeared gratified with the distinction, and willingly adopted the title. Even Constantine himself, when he was emperor, accepted it, although he was seduced from the path of rectitude in regard to sacred affairs and had embraced the Christian faith. In like manner did all who succeeded him to Valentinian and Valens.
[4.36.5] But when the pontifices, in the accustomed manner, brought the sacred robe to Gratian, he, considering it a garment unlawful for a Christian to use, rejected their offer. When the robe was restored to the priests who brought it, their chief is said to have made this observation, "if the emperor refuses to become pontifex, we shall soon make one."