Definition: To bring up an issue that has already been concluded; something that's considered to be pointless.Origin: This phrase may originate with horse racing, where horses are sometimes "beaten" by their riders to get them moving faster. If the horses were dead, then there wouldn't really be much of a point in beating them. Thus, the pointlessness of beating a dead horse would eventually go on to apply to other things.Some scholars claim that the phrase originated in 17th-century slang, where a "dead horse" was work that was paid for in advance, e.g. "His land 'twas sold to pay his debts; All went that way, for a dead horse, as one would say. "This attribution confuses "flogging a dead horse" with an entirely different phrase: "to work (for) the dead horse". Most men paid in advance apparently either wasted the money on drink or other such vices, or used it to pay outstanding debts.