true origin

The word "priest" is the Anglo-Saxon translation of the Greek "presbyteros."

From the OED:

OE. préost = OHG. prêst, priast, ON. prest-r (Norw. prest, Sw. präst, Da. præst); app. shortened from the form seen in OS. prêstar, OHG. prêstar, priestar (MDu., Du., MHG., Ger. priester), OFris. prêstere; ultimately from L. presbyter (-biter), a. Gr. elder: see PRESBYTER; perh. immediately through a Com. Romanic *prester (whence OF. prestre, F. prêtre, Sp. preste, It. prete). The origin of éo in OE. préost, and the anterior phonetic history of this and the other monosyllabic forms, are obscure; see Pogatscher Lehnworte im Altengl. §142. The ON. may have been from OLG. or OE.

From this site:

O.E. preost, shortened from the older Gmc. form represented by O.S., O.H.G. prestar, O.Fris. prestere, from V.L. *prester "priest," from L.L. presbyter "presbyter, elder," from Gk. presbyteros (see Presbyterian). In O.T. sense, a transl. of Heb. kohen, Gk. hiereus, L. sacerdos. Priesthood is O.E. preosthad. Priestcraft originally was "the business of being a priest" (1483); after rise of Protestantism and the Enlightenment, it acquired a pejorative sense of "arts of ambitious priests for temporal power and social control" (1681).

So much for the theory that priests are not presbyters because they have different names.