Английский Этимологический словарь - cock (n.)

- O.E. cocc, O.Fr. coq, O.N. kokkr, all of echoic origin. O.E. cocc was a nickname for "one who strutted like a cock," thus a common term in the Middle Ages for a pert boy, used of scullions, apprentices, servants, etc. A common personal name till c.1500, it was affixed to Christian names as a pet diminutive, cf. Wilcox, Hitchcock, etc. Slang sense of "penis" is attested since 1618 (cock-teaser is from 1891). Cocky "arrogantly pert" (1768) originally mean "lecherous" (16c.), modern sense of "vain" is 18c. A cocker spaniel (1823) was trained to start woodcocks. Cock of a faucet first recorded c.1425; of a gun, 1566, hence half-cocked "with the cock lifted to the first catch, at which position the trigger does not act." Cock-and-bull is first recorded 1621, perhaps an allusion to Aesop's fables, with their incredible talking animals, or to a particular story, now forgotten. Fr. has parallel expression coq-а-l'вne.