E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
properly means a man (Old High German, baro). It was a term applied to a serving-soldier, then to a military chief, and ultimately to a lord. The reverse of this is seen in our word slave (a servile menial), which is the Slavonic word slav (noble, illustrious). Barones vel varrones dicuntur servi militum, qui utique stultissimi sunt servi videlicet stultorum. (Scholiast.) (See IDIOT.)