Plumer la poule sans la faire crier

Literally: To pluck the hen without making her cry

Example: “Avec ses petits frais cachés, la banque plume la poule sans la faire crier.” — With its little hidden fees, the bank fleeces its customers without them ever noticing.

Origin: The Académie française's first dictionary (1694) already defines plumer la poule sans crier (to pluck the hen without its squawking) as exacting what is not owed "skillfully, without noise or fuss," and its 1762 edition adds that soldiers "pluck the hen" when they go foraging at the peasants' expense. Plucking the bird so smoothly that it never protests is the refinement. Stendhal wrote in 1818 that Napoleon's secretary of state, the duc de Bassano, chose prefects for exactly that talent. A similar maxim about plucking a goose is often credited to Colbert, Louis XIV's finance minister, but the attribution is unconfirmed.