firedamp
The old mining term for explosive gases in coal mines is "firedamp". It seems illogical - I mean, a damp fire? - until you realize that it comes from the German word "dampf" for vapors.
There are other "damps" in mining terminology - "afterdamp", for instance, refers to the poisonous gas carbon monoxide, which tends to build up in mines after an explosion. But firedamp explicitly refers to a gas mixture rich in the flammable gas methane, which - as the recent disaster in West Virginia's Upper Branch Mine reminds us - burns like a devil's torch. Twenty-five miners were killed outright in the…