Neatsfoot oil is a yellow oil rendered and purified from the shin bones and feet (but not the hooves) of cattle. "Neat" in the oil's name comes from an old English word for cattle. Neatsfoot oil is used as a conditioning, softening and preservative agent for leather.
Yep. Used it all the time to winterize my hunting boots back in the day when boots were actually made of leather.
I did learn that thanks, when I looked up info about it, to try to find if it is still in use. ;D