magistrate (n.)

late 14c., "a civil officer in charge of administering laws," also "office or function of a magistrate," from Old French magistrat, from Latin magistratus "a magistrate, public functionary," originally "magisterial rank or office," from magistrare "serve as a magistrate," from magister "chief, director" (see master (n.)). From late 17c. often meaning "justice of the peace" or other minor officials having criminal jurisdiction.