Why is the ninth month called September?
early 14c., "grow, sprout, blossom," from Anglo-French burjuner, Old French borjoner "to bud, sprout," from borjon "a bud, shoot, pimple" (Modern French bourgeon), of uncertain origin. Perhaps from Vulgar Latin *burrionem (nominative *burrio), from Late Latin burra "flock of wool," itself of uncertain origin. Some sources (Kitchin, Gamillscheg) say either the French word or the Vulgar Latin one is from Germanic. The English verb is perhaps instead a native development from burjoin (n.) "a bud" (c.1300), from Old French. Related: Burgeoned; burgeoning.