Why is the ninth month called September?
c.1300, of unknown origin, not in Old English; perhaps from Old French (Flanders dialect) purer "to sift (grain), pour out (water)," from Latin purare "to purify," from purus "pure" (see pure). Replaced Old English geotan. Intransitive sense from 1530s. Related: Poured; pouring; pourable. As a noun from 1790.