Why is the ninth month called September?
Old English windwian, from wind "air in motion, paring down," see wind (n.1). Cognate with Old Norse vinza, Old High German winton "to fan, winnow," Gothic diswinþjan "to throw (grain) apart," Latin vannus "winnowing fan."
Corn was winnowed, (1.) By being thrown up by a shovel against the wind. As a rule this was done in the evening or during the night, when the west wind from the sea was blowing, which was a moderate breeze and fitted for the purpose. The north wind was too strong, and the east wind came in gusts. (2.) By the use of a fan or van, by which the chaff was blown away (Ruth 3:2; Isa. 30:24; Jer. 4:11, 12; Matt. 3:12).