'afterdamp' originates from the combination of 'after' and 'damp', where 'damp' referred to a noxious gas in mining contexts.

'damp' was used in Middle English to describe harmful gases in mines, and 'afterdamp' evolved to specify the gases present after an explosion.

Initially, 'damp' referred to any harmful gas, but 'afterdamp' became specific to post-explosion gases in mines.