I have Appalachian-American kinfolk. I was always taught all y'all is for 5 or more. Persons, not an aggregate total of teeth.
I'm from the deep south, and I can assure you that, while yall
always means more than one, it doesn't have to mean more than two. However, it can refer to non-present entities, which often leads to confusion amongst outsiders.
An example might be:
Flight instructor comes into the FBO while student is post-flighting.
Me: "How was it up there?"
He: "A little bumpy, but decent above 2,000'"
Me: "Yall up at Dothan today?"
He: "Naw, we were working on diversions around Marianna."
Me: "Oh, gotcha. Hey, I've been meaning to ask—how're your folks doing with all that flooding?"
He: "Aw, man... So Carl knows a fellow from Wausau runs a cleanup business on the side. I called him up, and he sent this kid down... laziest worker I've ever seen in my life. Two days and he hasn't even finished the living room. I'm fixing to call up a professional service for the sofa and beds, but that's gonna be at least four times what I was gonna pay."
Me: "Damn. Man, I didn't realize yall got hit that bad. That was all from the river swamp?"
He: "Well, it was a scary couple days. All yall up in the sand hills wouldn't have seen much, but we're in a clay basin down there, so when we get a lot of rain, ain't nowhere for it to go but up."
Me: "If you don't mind me asking, why on earth are they building 'em all out there?"
He: "Don't even get me started. Arvida went and—"
Sorry, got a little carried away there... hopefully that helps a little with a slightly-less-than-completely-artificial-example of the myriad uses of yall.
~Fox
I don't have any kin missing significant numbers of teeth in this enlightened age, I might add.