"I seen thrashin' machines on the way down. That means we'll be bucking grain bags"

Threshing machines, originally known as "thrashing machines", were used in grain crop farming to cut the heads of grain off the straw, remove the grain from the heads, and sack the grain. Men then had to "buck", or load, the bags of grain onto wagons or trucks.

Today, the same process is normally performed by a combine harvester, which also reaps the crop.

 

For the 1939 movie Of Mice and Men, Aaron Copland composed a piece entitled "Threshing Machines":