To lose leather; to be galled with riding on horseback, or, as the Scotch express it, to be saddle sick. To leather also meant to beat, perhaps originally with a strap: I’ll leather you to your heart’s content. Leather-headed; stupid. Leathern conveniency; term used by quakers for a stage-coach.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Least In Sight * LeeryNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes