Prester John Look up Prester John at Dictionary.com
c.1300, Prestre Johan, legendary medieval Christian king and priest, said to have ruled either in the Far East or Ethiopia. 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 culturally backwards and militarily threatened, dreaming of a mythical deliverer. Compare Old French prestre Jehan (13c.), Italian prete Gianni.