Winnowing is the agricultural process of separating grain from chaff by moving air. The grain is distinguished from lighter refuse through the action of wind or a fan. It is associated with the related agricultural activities of threshing and the use of a fan.
The supplied material identifies winnowing with the biblical subjects of agriculture, the fan, and threshing. These associations present it as an ordinary farming operation used to separate useful grain from chaff.
No additional historical background is supplied beyond the connection of winnowing with ancient agricultural practice, threshing, and the fan used in the separation process.