Beat a dead horse
This phrase is generally believed to come from the 19th century, when beating a horse to make them go faster was common.
Logically, beating a dead horse is a pointless activity as it can’t move. The idiom appeared in 1859, in the London-based newspaper ‘Watchman and Wesleyan Advertiser’, where it said: ‘It was notorious that Mr. Bright was dissatisfied with his winter reform campaign and rumour said that he had given up his effort with the exclamation that it was like flogging a dead horse.’
However, some scholars consider it to have originated even earlier, in the 17th century, where it was known as ‘flogging a dead horse’. Today, both ‘beat a dead horse’ and ‘flogging a dead horse’ can be used.
I don’t mean to beat a dead horse but can you explain the situation to me again?
Re-counting the votes of an election can be like beating a dead horse sometimes.
He keeps trying to get his novel published but it’s been rejected twelve times already. It’s like beating a dead horse, but he won’t give up.