What does "talk turkey" mean?

Speak plainly, get to the point, as in Don't call me until you're ready to talk turkey. This expression allegedly comes from a tale about an Indian and a white man who hunted together and divided the game. When the white man said, “I'll take the turkey and you the buzzard, or you take the buzzard and I the turkey,” the Indian replied, “Talk turkey to me.” Whether or not this tale had a true basis, the term was recorded in its present meaning by about 1840.