I never heard these as a string- just one or two- but i suspect that
L for leather [which is silly really, as L is for leather]
is bassed on Hell for Leather-- which is an idiom that means go at something, no matter what--

"The shoppers went hell for leather to get the last few pieces, of the last shipment of the latest electronic toy, before the stores closed for the holidays"

In an other thread, Rodward, and others shared other versions.


my other obsession