Online Etymology Dictionary
1541, "guinea fowl" (Numida meleagris), imported from Madagascar via Turkey, by Near East traders known as turkey merchants. The larger North American bird (Meleagris gallopavo) was domesticated by the Aztecs, introduced to Spain by conquistadors (1523) and thence to wider Europe, by way of North Africa (then under Ottoman rule) and Turkey (Indian corn was originally turkey corn or turkey wheat in Eng. for the same reason). The word turkey was first applied to it in Eng. 1555 because it was identified with or treated as a species of the guinea fowl. The Turkish name for it is hindi, lit. "Indian," probably via Fr. dinde (contracted from poulet d'inde, lit. "chicken from India"), based on the common misconception that the New World was eastern Asia. The New World bird itself reputedly reached England by 1524 (when Henry VIII is said to have dined on it at court). Turkeys raised by the Pilgrims were probably stock brought from England. 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 ref. to marksmanship contests where turkeys were tied behind a log with their heads showing as targets.