Wind winnowing is an agricultural method developed by ancient cultures for separating grain from chaff. It is also used to remove hay and chaff or other pests from stored grain. Threshing, the loosening of grain or seeds from the husks and straw, is the step in the chaff-removal process that comes before winnowing.
After a flail had separated the grain from the harvested sheaves, a winnowing basket was used to separate the corn kernels from the outer husks or chaff. The thrashed corn was thrown up from the basket and the breeze (sometimes created by waving a sheet) blew the chaff from the heavier kernels.