An Etymological Dictionary of the German Language/Annotated/braun
braun, adjective, ‘brown,’ from Middle High German brûn, ‘brown, dark-coloured, shining, sparkling,’ Old High German brûn; compare the corresponding Dutch bruin, Anglo-Saxon brûn, English brown, Old Icelandic brúnn. This Teutonic term passed into Romance (compare the cognates of Italian bruno, French brun; see Blond); hence also Lithuanian brunas, ‘brown.’ The proper stem of Aryan bhr-ûna-, appears in Lithuanian beras, ‘brown’ (compare Bär), and reduplicated in Old Indian babhrú-s, ‘reddish brown, bay’ (this form of the adjective being apparently a common Aryan term for a brownish mammal living in water; compare Biber); hence it may be right to assign Greek φρύνη, φρῦνος, ‘toad,’ to this root. Respecting Braun as a name for the bear, see Bär. —