Prester John Etymology
According to SIlverberg (p. 319),
Explaining 'Prester' in a roundabout fashion still begged the question of the derivation of 'John,' unless one accepted the 1533 'gyam' etymology. Soon the 1533 explanation was confirmed by Portuguese returning from Ethiopia, who reported that the natives did indeed call their king by a title variously transcribed as 'jan,' 'gian,' or 'zan,' which meant "powerful" and was pronounced "zhan." That seemed to settle the issue. 'Jan Belul,' which could be translated as 'Precious John,' was the Ethiopian appelation of rank that had found its way into European tongues as "Prester John."
Pero Paez suggests instead that the Ethiopian king possibly became known as Prester John
due to the fact that as the Emperor is usually a deacon, some Greeks call in Presbyter, and then adding to this the title of 'zan,' which... is given to the Emperor, they came to say 'Preste zan, and foreigners, who are often wont to corrupt names... thus called him Prester John. This name Zan is of ancient usage in Ethiopia [and]... is still employed; for they speak of the officials of 'zan,' as we should say officials of the Emperor (qtd. in Silverberg, p. 319).
Manoel de Almeida begins his High History of Ethiopia or Abassia with a chapter called "The Name Prester John," in which he reports the familiar narrative that the title Prester John was misattributed to the Ethiopian King by Covilhã. As recorded in Silverberg (p. 320), Almeida notes that the name
was at first given to a Christian, but Nestorian, emperor who ruled in the interior of Asia. His ordinary name or title was Jonanam, derived from the prophet Jonah (this name has been erroneously changed by Europeans into John). THis name was common to the rulers of that monarchy as that of Pharaoh was to the Kings of Egypt. They called him Presbyter because of the cross that he always carried aloft before him, as among us Archbishops and Primates do.
