Threshing or thrashing is the process of loosening the edible part of grain (or other crop) from the straw to which it is attached. It is the step in grain preparation after reaping. Threshing does not remove the bran from the grain.

Before the practice was mechanized, threshing was a time-consuming and laborious practice, taking up as much as one-quarter of agricultural labour in the 18th century. With the implementation of a flail, or pair of connected sticks, non-mechanized threshing could yield around 8 bushels of wheat, 30 of oats, 16 of barley, 20 of beans, 8 of rye and 20 of buckwheat per day, respectively.

https://en.wikipedia.org/wiki/Threshing