"To talk turkey
" is a term meaning to talk in a straightforward and serious fashion.
Originally, the expression was used to describe a pleasant conversation. A young man said, or talked, turkey to an attractive girl, if he had the chance. Perhaps that was because a young man in such a situation might get so tongue-tied that his speech could be likened to the gobbling of a turkey.
Sometime around the turn of the century, through an uncertain process, it came to hold its current meaning.
There is a (variously reported and somewhat racist) legend that is often used as an explanation of the way this expression arose:
Two men, one an Indian, went for a day's hunting. They shot several birds, among them one or more turkeys; but when it came time to divide the bag, the smart white man, thinking to take advantage of an ignorant savage, always arranged the counting in such a way that he got the greater amount. The Indian, however, was not so gullible as he seemed. Finally he faced his companion. "Ugh," he said, "All time you talk turkey. Now I talk turkey to you."