Question

The term used for the process of seperation of grains from chaff is threshing whereas winnowing does the same task. So why is it that the term used is threshing and not winnowing?

Answer 1

Threshing is the process of loosening the edible part of grain (or other crop) from the husks and straw to which it is attached. It is the step in grain preparation after reaping and before winnowing, which separates the grain from the chaff. Threshing does not remove the bran from the grain.[1]
Threshing may be done by beating the grain using a flail on a threshing floor. Another traditional method of threshing is to make donkeys or oxen walk in circles on the grain on a hard surface. A modern version of this in some areas is to spread the grain on the surface of a country road so the grain may be threshed by the wheels of passing vehicles.
Hand threshing was laborious, with a bushel of wheat taking about an hour.] In the late 18th century, before threshing was mechanized, about one-quarter of agricultural labor was devoted to it.
Industrialization of threshing began in 1786 with the invention of the threshing machine by Scotsman Andrew Meikle. Today, in developed areas, it is now mostly done by machine, usually by a combine harvester, which harvests, threshes, and winnows the grain while it is still in the field.
The cereal may be stored in a barn or silos.
A threshing bee was traditionally a bee in which local people gathered together to pitch in and get the season's threshing done. Such bees were sometimes festivals or events within larger harvest festivals. Today the original purpose is largely obsolete, but the festival tradition lives on in some modern examples that commemorate the past and include flea markets, hog wrestling, and dances.

Wind winnowing is an agricultural method developed by ancient cultures for separating grain from chaff. It is also used to remove weevils 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.
In its simplest form it involves throwing the mixture into the air so that the wind blows away the lighter chaff, while the heavier grains fall back down for recovery. Techniques included using a winnowing fan (a shaped basket shaken to raise the chaff) or using a tool (a winnowing fork or shovel) on a pile of harvested grain..