Why was "tantrum" trending last week?
c.1300, "the husk of wheat, barley, etc., separated from the flour after grinding," from Old French bren "bran, scurf, scales, feces" (12c., Modern French bran), perhaps connected with Gaulish *brenno- "manure," or with burn (v.). The word also was used 16c. in English for "dandruff flakes."
The outer layers of a cereal grain such as wheat, approximately 20 percent of which is indigestible cellulose, used as a source of dietary fiber.