old chestnut

Etymology
Originally as, with “old” for emphasis. Popularized US 1880s, particularly Northeast and Midwest, with various theories propounded.

A commonly cited theory, viewed by the Oxford English Dictionary as “plausible” and cited by Brewer’s, is that it was coined by Boston comedic actor William Warren Jr., quoting from 1816 English melodrama The Broken Sword by. One of the characters in the play is a boor, and when once recounting a tale mentions a cork tree, which is corrected by the character Pablo as “A chestnut. I have heard you tell the tale these 27 times.” This line was then apparently quoted at a dinner party by Warren in response to a boor there, and proved popular. Note that William Warren Sr. had previously played Pablo on stage, but died in 1832, so the phrase was presumably popularized by the son, William Warren Jr.

Noun

 * 1)  A well-worn story.

Usage notes
Often used disapprovingly, to imply “a tired old story”, but also used approvingly to introduce an aphorism – “as the old chestnut goes, …”.