slush fund (money stored for illegal or dishonest purposes)
çekim: çoğul caisses noires
eş: boîte à Perrette
köken: The term dates from the first half of the 19th century, stemming from near-clandestine efforts by railway workers at improvised health insurance, for which they would pass around a black crate, to which each worker would contribute. See the French Wikipedia article for more information.