Green’s Dictionary of Slang

1. the buttocks.

1966

Trimble 5000 Adult Sex Words and Phrases.

2. a piece of bacon thrown out as unsaleable by the grocer or butcher.

1939

J. Worby Spiv’s Progress 9: He had the usual tramp’s hand-out of chin straps and cat’s-meat - in other words pieces of bacon and meat that the grocer and butcher don’t want .