priest (n.)

c. 1300, Prestre Johan, legendary medieval Christian king and priest, said to have ruled either in the Far East or Ethiopia. Prestre (attested as a surname late 12c.) is from Vulgar Latin *prester, a transition between Latin presbyter and English priest. First mentioned in the West by mid-12c. chronicler Otto of Freising, who told how Johannes Presbyter won a great victory over the Persians and the Medes. Between 1165 and 1177 a forged letter purporting to be from him circulated in Europe. All this recalls the time when the Christian West was militarily threatened on its frontiers by Muslim powers, dreaming of a mythical deliverer. Compare Old French prestre Jehan (13c.), Italian prete Gianni.

late 15c., "business of being a priest, exercise of priestly functions," from priest + craft (n.). After rise of Protestantism and the Enlightenment, it acquired a pejorative sense of "arts and devices of ambitious priests for attaining and holding temporal power and social control" (1680s).