Avoir d'autres chats à fouetter

Literally: To have other cats to whip

Example: “Désolé, je ne peux pas t'aider ce soir, j'ai d'autres chats à fouetter.” — Sorry, I can't help you tonight; I have bigger fish to fry.

English equivalent: To have bigger fish to fry

Origin: Grows out of the older il n'y a pas de quoi fouetter un chat (there's nothing here worth whipping a cat over, meaning the fault is trivial), both attested from the 17th century. Why a cat specifically nobody has ever nailed down, and the sources are refreshingly candid about it: swap in almost any other small task — peeling potatoes, laying tiles — and the joke would work exactly as well. Alain Rey proposes that fouetter is a comic deformation of the cruder foutre, with chat meaning female anatomy rather than the animal, which would put the phrase in the same family as a great deal of French wordplay that runs sex through a barnyard — but by his own admission it doesn't explain the cat either. The English parallel, to have other fish to fry, is often pointed out as the tidier version: a fish belongs in a pan in a way a cat never belongs under a whip.