Why do country folk add "boy" or "girl" after saying a person's name?

“Way to go, Dana-girl!” Or “That’s it, Sammy-boy.”

I’ve always wondered why do they say it, I mean yes it’s a southern thing but why though? Does it mean like some sort of term of affection/endearment? Or do they say it just because? If anyone knows, I’d appreciate it, thanks!