firedamp means A flammable gas (mostly methane) found in coal mines; forms an explosive mixture with air. Lexicurio rates it Sui generis — a strength score of 88 out of 100.
Etymology
From fire + damp with 'damp' not in the usual sense of 'moist' but old German, modern Dutch, Danish 'damp' as steam or vapour, hence a gas liable to catch fire.
noun
- A flammable gas (mostly methane) found in coal mines; forms an explosive mixture with air.
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