Le torchon brûle

Literally: The dishcloth is burning

Example: “Depuis les vacances, le torchon brûle entre les deux amoureux.” — Since the vacation, there's been trouble in paradise for the two lovebirds.

English equivalent: Trouble in paradise

Origin: The modern picture is a domestic scene, a tea towel catching fire on the stove and a row starting immediately, which is a fine image and is not where the phrase comes from. It dates to the end of the 18th century, and in it torchon is not a kitchen cloth. The word's earliest sense, in the 12th century, was a blow — a hit — which puts the fight in the phrase from the start; a coup de torchon is still a brawl and a torchée is still a thrashing. The Académie's 1798 dictionary takes a different line, glossing torchon here as torche, a burning brand, so that the discord is literally alight. Claude Duneton proposes both at once, as a double pun: torcher in the sense of trading blows, plus the brûler children use in hide-and-seek, where you are told tu brûles as you get close to the hidden thing. On that reading, the dishcloth is burning means the blows are getting very near. Perfectly clear.