cauldron bottom

English

Etymology

From cauldron +‎ bottom, in reference to the shape and colour as seen from the perspective of someone in the coal mine. Compare Sicilian campanaru (literally “bell tower”) in sulfur mining.

Noun

cauldron bottom (plural cauldron bottoms)

1. (UK, mining slang, obsolete) A large, round mass in a coal seam that forms part of the roof of a coal mine passage (usually being a fossilized root or stump); considered a hazard due to being prone to falling without warning.

   Synonym: (vulgar) cauldron arse

2. Used other than figuratively or idiomatically: see cauldron,‎ bottom.