black box, flight recorder · black box (device or program with known inputs and outputs but unknown method of operation) · Used other than figuratively or idiomatically: see czarna, skrzynka.
A black box: a device that records the activity data of an aircraft or other vessel. · A black box: a device whose input and output characteristics are known but whose internal workings are unknown or ignored.
köken: From קופסה (kufsá, “box”) + שחורה (sh'khorá, “black”), hence literally “black box”; a calque of English black box.