This is an incorrect definition of Rat Killing
When dad has unruly boys needing something to do, he'll say "Boys, there's too many rats down in the barn, we need to kill them." Gets boys up in the middle of the night and they kill rats with shotguns.
Of course, there's always just as many rats down at the barn..
By extension, a "rat killing" job is one designed to kill time but which doesn't have any net effect accomplishing anything...
by Sam Fullman on Aug 20, 2015