mole [OE] English has several unrelated words spelled mole. The oldest refers to a small blemish on the skin; in Old English this meant ‘a discoloured spot on cloth’. Next to appear was the mole [LME] that now means ‘a structure serving as a pier, breakwater, or causeway’, which goes back to Latin moles ‘mass’ (the earliest sense in English) which also lies behind demolish [M16th]. The mole that is a burrowing animal stayed underground until the later Middle Ages, and went under other names before then—in Old English it was a want, and then also a mouldwarp. The novels of John le Carré popularized the term mole for a spy who gradually achieves an important position within the security defences of a country: it first appeared in Tinker, Tailor, Soldier, Spy in 1974. The world of espionage seems to have adopted the use from le Carré, rather than vice versa. See also mountain.