Now wait a minute. As a resident of the Show-Me state I doth protest. :) As I understand it, "y'all" is the second person SINGULAR pronoun. The second person plural pronoun is "all y'all". :)
Where I learned my southern was in Mississippi and I was firmly told, well, I was firmly told a lot of things that we need not go into here. But "y'all" (they said) is plural. "All y'all" is, like a plural intensive general, as opposed to "each one of y'all" .
And here in the Old Dominion, which Mississippi considers to be the North, the usage is the same.
Dang pesky border states!
Daddy? Is it time to tell them you were born in Indiana and brung up in Long Island, NY?
You hush up now, littl'un.
LOL Touche