To flog a dead horse means to keep trying to revive interest in something that has already died out, or to keep putting effort into a cause that has plainly gone nowhere. It is said of arguments repeated long after everyone has stopped listening, of projects kept going well past the point of any use, of any attempt to squeeze more out of something that has nothing left to give. The picture behind it is straightforward: a carter beating an animal that is already dead, in work that cannot possibly make it move faster, or at all.
What’s the origin of the phrase ‘flog a dead horse’?
The earliest print use so far found for the phrase in its current sense comes from a report of a House of Commons debate in 1859. Lord Elcho, discussing a saying attributed to the politician John Bright, told the House that Bright had said he found he was “flogging a dead horse.” Whether Lord Elcho coined the phrase himself or was repeating something already heard elsewhere cannot be established, since no earlier printed instance of it has come to light.
The image of a dead horse standing for wasted effort is older than that debate, though earlier examples use it differently. In Richard Brome’s play The Antipodes, first performed in 1638 and printed in 1640, a character describes property sold to pay off debts as going “that way for a dead horse,” meaning the money was already gone with nothing to show for it. In the seventeenth century, gamblers spoke of “playing for a dead horse” when staking money on a bet already effectively lost, recorded in an account of Sir Humphry Foster’s estate being recovered by “happy fortune” after such a wager. Journeymen printers of the eighteenth and nineteenth centuries used “horse” for work already paid for in advance, so finishing it was called “working for a dead horse,” since no further benefit would come to the labourer from doing it.
These older uses share the same image but not quite the same meaning as the modern idiom. It is only with Lord Elcho’s 1859 remark that the phrase settles into the sense used today, of persisting with something unmistakably finished, much like continuing to argue with something as dead as a doornail.