Flogging a dead horse is an idiom that means a particular effort is a waste of time as there will be no outcome, such as in the example of flogging a dead horse, which will not cause it to do any useful work.
Earliest use
According to the Oxford English Dictionary, the first recorded use of the expression in its modern sense was by the English politician and orator John Bright in reference to the Reform Act of 1867, which called for more democratic representation in Parliament. Trying to rouse Parliament from its apathy on the issue, he said in a speech, would be like trying to "flog a dead horse" to make it pull a load. The Oxford English Dictionary cites usage in The Globe in 1872 as the earliest verifiable use of "flogging a dead horse", where someone is said to have "rehearsed that lively operation known as flogging a dead horse". However an earlier instance is attributed to that same John Bright thirteen years prior: speaking in Commons on suffragette protests, March 28, 1859, Lord Elcho remarked that Bright had not been "satisfied with the results of his winter campaign" and that "a saying was attributed to him that he found he was 'flogging a dead horse'."
Earlier meaning
Some scholars claim that the phrase originated in 17th-century slang, when a horse was a symbol of hard work. Paying for such hard work in advance meant the chances of a horse's work being done, rather than simply keeping the payment, could be represented by a dead horse. In a seventeenth century quote from a collection of documents owned by the late Earl of Oxford, Edward Harley,
Foster apparently "played for" the dead horse by seeking payment for work without working, and regained his fortune by finding it. Many sailors were paid in advance for their first month's work. In his book Old England and New Zealand, author Alfred Simmons gives detailed explanation and background of the "Flogging the Dead Horse" ceremony, performed by a ship's crew at the end of the first month of their voyage at which time wages resumed. The sailors would get paid in advance of leaving the harbour, spend their money, and embark the ship with nothing. This situation allowed them to exclaim the horse symbolising their usual hard work, without money for motivation, was dead. However, once a month had passed, the sailors would have reached the Horse latitudes where wages due and paid would prompt the horse to live again. One of the earliest synonyms may be found in an ancient Greek play by Sophocles, Antigone,
