Why is the ninth month called September?
late 13c., probably from Old Norse hvirfla "to go round, spin," related to hvirfill "circle, ring, crown," and to Old English hweorfan "to turn" (see whir). Related: Whirled; whirling. Whirlybird "helicopter" is from 1951.
early 15c., "flywheel of a spindle," from whirl (v.). The meaning "act of whirling" is recorded from late 15c.; figurative sense of "confused activity" is recorded from 1550s. Colloquial sense of "tentative attempt" is attested from 1884, American English.