Easton’s Bible Dictionary

Winnow : 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; Isaiah 30:24; Jeremiah 4:11,12; Matthew 3:12).