In the earliest attestations of the word priest back in Old English, it was spelled preost. As the language developed into Middle English, we started getting forms like preast, prest, preiste, preyste, and more, with the modern spelling becoming the standard sometime in the seventeenth century. The word comes from the Late Latin word presbyter, meaning “elder”, and that comes from Ancient Greek presbyteros, the comparative word for “old”, presbys. Finally, there are several theories as to where the Greek word comes from. The most accepted explanation is that pres- means “before” or “in front” (from the Proto-Indo-European root per, “forward”) and that bys might be from bous, “cow”. Either way, as you may have guessed, priest is related to the word presbyterian, which is pretty cool.
