I am fond of saying this phrase, when I want to describe a breed of hussy with colossal, ferocious sweater kittens. People used it often in the region where I grew up (the deep south) to communicate this largesse of breast in a kindly, non-offensive and almost admiring tone and manner.
The particular dialect I grew up with is a Delta twang, which has it's drawbacks (it's not the charming Carolina lilt you may be thinking of), but it is such that the delivery was in a rhythm that seemed to map to the not so gentle slope of a large teat.
You'd see a Pam Anderson, or a Hattie McDaniel, or an average grandma walk by and raise your eyebrows while looking at a space somewhere to the left of your feet, on the ground. "Damn. She got TIIIIG ole bitties." The tiiiig was drawn out so that your neck often pushed your head forward, chicken-like, for a moment as you ruminated on how tig they really were. Ole Bitties was pronounced practically as one word, and you drew your head back to it's normal position, keeping your eyes carefully averted from addressing the bitties directly. Try it at home.
I googled "Tig Ole Bitties" and it turns out it's quite popular, with it's own Urban Dictionary definition, a porn movie starring some black chicks, and even a t-shirt. Which I might have to buy.