English, Scottish, and Irish: generally a nickname referring to
the color of the hair or complexion, Middle English br(o)un,
from Old English brūn or Old French brun. This word is
occasionally found in Old English and Old Norse as a personal
name or byname. Brun- was also a Germanic name-forming element.
Some instances of Old English Brūn as a personal name may
therefore be short forms of compound names such as Brūngar,
Brūnwine, etc. As a Scottish and Irish name, it sometimes
represents a translation of Gaelic Donn. As an American family
name, it has absorbed numerous surnames from other languages
with the same meaning.