An Etymological Dictionary of the German Language/Annotated/Baron
Baron, masculine, ‘Baron,’ not from the equivalent Middle High German barûn, but from the French and MidL Rhenish form baron, which is found in the 16th century; Middle Latin baro, baronis, is by some based on Keltic bar, ‘man,’ and by others on Anglo-Saxon beorn or on Old High German baro, ‘man, vassal.’