beat a dead horse

Idioms  

1. Also, flog a dead horse. Try to revive interest in a hopeless issue. For example, Politicians who favor the old single-tax idea are beating a dead horse. From the 1600s on the term dead horse was used figuratively to mean “something of no current value,” specifically an advance in pay or other debt that had to be worked (“flogged”) off. [Second half of 1800s]

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Example Sentences

“I don’t want to beat a dead horse, but we tried like heck to acquire Khalil Mack,” Lynch said in an interview with 95.7 The Game last month.

From Los Angeles Times • Dec. 17, 2018

Aronofsky’s point was made about an hour into the film, but he proceeded to beat a dead horse for the remaining hour.

From New York Times • Sep. 20, 2017

“I’m not going to beat a dead horse, man,” Newton said.

From Washington Post • Dec. 20, 2016

As Malofiy continued to ask Page whether he had ever talked about being a fan of Spirit, Judge Klausner interrupted, saying: "How many times can we beat a dead horse?"

From BBC • Jun. 16, 2016

Only if you’re Roger Federer. beat a dead horse.

From "Woe Is I" by Patricia T. O'Conner