1540s, originally "guinea fowl" (Numida meleagris), a bird imported from Madagascar via Turkey, and called guinea fowl when brought by Portuguese traders from West Africa. The larger North American bird (Meleagris gallopavo) was domesticated by the Aztecs, introduced to Spain by conquistadors (1523) and thence to wider Europe. The word turkey first was applied to it in English 1550s because it was identified with or treated as a species of the guinea fowl, and/or because it got to the rest of Europe from Spain by way of North Africa, then under Ottoman (Turkish) rule. Indian corn was originally turkey corn or turkey wheat in English for the same reason.
The Turkish name for it is hindi, literally "Indian," probably influenced by French dinde (c. 1600, contracted from poulet d'inde, literally "chicken from India," Modern French dindon), based on the then-common misconception that the New World was eastern Asia.
After the two birds were distinguished and the names differentiated, turkey was erroneously retained for the American bird, instead of the African. From the same imperfect knowledge and confusion Melagris, the ancient name of the African fowl, was unfortunately adopted by Linnæus as the generic name of the American bird. [OED]
The New World bird itself reputedly reached England by 1524 at the earliest estimate, though a date in the 1530s seems more likely. The wild turkey, the North American form of the bird, was so called from 1610s. By 1575, turkey was becoming the usual main course at an English Christmas. Meaning "inferior show, failure," is 1927 in show business slang, probably from the bird's reputation for stupidity. Meaning "stupid, ineffectual person" is recorded from 1951. Turkey shoot "something easy" is World War II-era, in reference to marksmanship contests where turkeys were tied behind a log with their heads showing as targets. To talk turkey (1824) supposedly comes from an old tale of a Yankee attempting to swindle an Indian in dividing up a turkey and a buzzard as food.
"without preparation," 1910; narrower sense of "withdrawal from an addictive substance" (originally heroin) first recorded 1921. Cold turkey is a food that requires little preparation, so "to quit like cold turkey" is to do so suddenly and without preparation. Compare cold shoulder. To do something cold "without preparation" is attested from 1896.