Undermine (v.) To sap or weaken, often gradually, imperceptibly, and/or fundamentally.

Other forms: underminer (n.)

Etymology: A classic of the Anglo-Saxon “Take two words and smack ’em together backwards” school of etymology, “to undermine” originally meant “to mine under”—i.e., to dig a tunnel beneath the wall of an enemy castle, so as to weaken its foundation and attack from below.

Notes: This being a rather underhanded tactic, the word still frequently connotes deceit, although it can also be relatively neutral: Although still fond of his theory, the paleontologist admitted that the new fossil evidence appeared to undermine it. However, an “underminer” is almost always an insidious character, as can be seen in sources ranging from 16th century moral philosophy: “The whole broode of..secret vnderminers, hipocrits, and double dealers” (Baldwin, 1564) to comic monologuist Mike Albo’s insufferable frenemy.