A slang term, which in sexual parlance refers to a male's testicles, though it has other meanings.
It has also been used in British slang for meaning when one is tired, they are knackered out, or are knackers.
"I am knackers from all that fucking."
It is also a slang term to refer to a place where horses are euthanized, when no longer of use, or are suffering from illness.
Generally where horses are sent, for use as food, or to be made into glue.
Can also refer to an Irish travelling community.