early 13c., "hook-shaped instrument or weapon," from Old Norse krokr "hook, corner," cognate with Old High German kracho "hooked tool," of obscure origin but perhaps related to a widespread group of Germanic kr- words meaning "bent, hooked." Meaning "swindler" is American English, 1879, from crooked in figurative sense of "dishonest" (1708). Crook "dishonest trick" was in Middle English.
A habitual or professional criminal; a consistently dishonest person: The chief said, ''I'm not a crook'' (1870s+)
verbTo steal: He crooked my socks (1940s+)
in brass musical instruments, detachable piece of metal tubing inserted between the mouthpiece and the main tubing or in the middle of the tubing to lengthen the air column produced. This manipulation allows the player to obtain notes not included in the harmonic series of the original air column. Crooks were in use at least by about 1600 and were used extensively by the late 18th century. They were superseded in the 19th century by valves, which, unlike crooks, allowed instantaneous changes in basic air-column pitch