Middle English: probably of Scandinavian origin and related to Swedish dank 'marshy spot'.

• damp from Middle English:

  We do not think of something damp as being dangerous, but the word originally meant a noxious gas. This use survives in firedamp (late 17th century), a name for methane gas, especially when it forms an explosive mixture with air in coal mines. Damp did not come to refer to wetness until the 18th century. The damp squib which failed to go off has probably always marred firework displays—a squib is a small firework that burns with a hissing sound before exploding. From the middle of the 19th century the phrase began to be used of situations and events that were much less impressive than expected. Nowadays, the phrase is sometimes heard as ‘damp squid’, people substituting a more familiar and more familiarly damp word for the rarer squib. See also fiasco, lead, lemon. Both damp and dank (Middle English) are Germanic in origin, but were not originally connected.