Today’s idiom: beating a dead horse
Meaning: fruitless or pointless effort
Origin: Originally “dead horse” meant a job that a person was paid in advance for and might have already spent. This meaning came from a play by Richard Brome, The Antipodes, first performed in 1638 and first printed in 1640. The phrase “flogging a dead horse” or “beating a dead horse,” was first seen in print in 1859 in the report of a UK parliamentary debate.