A stale joke, anecdote, or adage. This term has a specific source, the play The Broken Sword by William Dimond, first produced in 1816. The principal character, a Captain Xavier, constantly repeats the same stories, one of which involves a cork tree. Pablo, another character, interrupts, saying, “Chestnut, you mean, captain. I have heard you tell the joke twenty-seven times, and I am sure it was a chestnut.” The play has long since been forgotten, but the term survives, and has itself become an old chestnut.

To do someone else’s dirty work. This term comes from an ancient fable in which a monkey, not wishing to burn its own fingers, persuades a cat to retrieve chestnuts that had fallen into the fire (whence also cat’s paw, for being made a dupe). Recounted in numerous early collections of fables (by La Fontaine, 1678, and Sir Roger L’Estrange, 1692, among others), it was transferred to any kind of dirty work by the eighteenth century.