Ass leather
From www.leather-dictionary.com - The Leather Dictionary
Ass leather is the term for a garment used by miners in past times as part of their gear. It was a belt-fastened leather apron, which was worn over the trousers and was supposed to protect the bottom, especially when the miner slipped through sliding shafts. Even today the ass leather can be seen as a part of the uniform in traditional miners' events.
Medieval miner slipping into a sloping chute on the ass leather.
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