The story
Compound of death + watch + beetle. The sound the beetles make is said to resemble a ticking watch, and is sometimes believed to herald death. Attested (as death watch) from the late 17th century.
Etymology from Wiktionary, CC BY-SA 4.0.
deathwatch beetle
Today it means: Any of various beetles of the family Anobiidae, now usually included in family Ptinidae, especially Xestobium rufovillosum, that bore into wood and make a tapping sound. Full definition →