premise: Also Went-worth/Flexner and Chapman both cite the term the leather as meaning a kick, but they date the term from 1946, citing a passage from Damon   he would give his fallen foe what we called `the leather,' meaning a few boots abaft the ears.
hypothesis: The phrase "the leather" means to give a friend one's extra cash (Went-worth/Flexner and Chapman, 1946).