Beat a dead horse

Meaning

Waste effort on something already decided.

Usage

Used to advise against rehashing settled matters.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Horse trading metaphor where flogging a dead animal is pointless.

19th-century American expression.