Why is the ninth month called September?
c.1600, from French bison (15c.), from Latin bison "wild ox," borrowed from Proto-Germanic *wisand- "aurochs" (cf. Old Norse visundr, Old High German wisunt "bison," Old English/Middle English wesend, which is not attested after c.1400). Possibly ultimately of Baltic or Slavic origin, and meaning "the stinking animal," in reference to its scent while rutting (see weasel). A European wild ox formerly widespread on the continent, including the British Isles, now surviving on forest reserves in Lithuania. Applied 1690s to the North American species commonly mis-called a buffalo.