Wild turkeys are indigenous to North America. When Europeans arrived, they at first mistook the turkeys they saw for guinea fowl, which were familiar to them, having been brought to Central Europe through the neighboring region of Turkey. Hence the name, which–as names sometimes do–outlasted its erroneous origin.
A better story though, recounted by Tad Tuleja in his fun book Fabulous Fallacies, credits the naming of the bird to Jose de Torres, the Portuguese Jewish interpreter of Columbus’s first journey, who upon seeing the first specimen of the bird in the New World is supposed to have cried out “Tukki, tukki!” which in Hebrew means “Big Bird.” Bon appétit. Or as Torres might have said: be’te-avon.