c. 1300, poucock, po-cok, "bird of the genus Pavo," especially an adult male, from Middle English po "peacock" + coc (see cock (n.)). Po is from Old English pawa "peafowl" (cock or hen), from Latin pavo (genitive pavonis), which, with Greek taos is said to be ultimately from Tamil tokei, but perhaps it is imitative: Latin represented the peacock's sound as paupulo. The Latin word also is the source of Old High German pfawo, German Pfau, Dutch pauw, Old Church Slavonic pavu. Middle English also had poun "peacock" from Old French paon.
Noted for its strutting gait, imposing magnificence, and the ostentatious displays of its beautiful tail, the peacock in his pride is one with his tail fully displayed. Used as the type of a vainglorious person from late 14c. (proud as a peacock). Its flesh superstitiously was believed to be incorruptible (even St. Augustine credits this). "When he sees his feet, he screams wildly, thinking that they are not in keeping with the rest of his body" [Epiphanus]. As a southern constellation from 1674.