There’s a Facebook group about the appropriate way to spell the contraction of “you all” so prevalent in the South.
The expression is y’all. Not ya’ll.
But there’s more to it than that. It’s also plural.
Yes, yes, I bet some of you Yankees have seen a Southerner appear to address a single person with the expression “y’all”. But, you really didn’t.
Example:
You’re waiting in line to pay your light bill, when someone in front of you is waving a receipt angrily and is saying, “Why did you turn of my lights? I paid y’all last week!”
The individual in question is not addressing the singular person behind the counter, but the entire company as represented by the customer service representative. In this case, the organization is a collective group of people appropriately addressed as “you all” or “y’all.”
If you are alone and are given the farewell, “Y’all come back now, y’hear?” you’re still not being addressed as “y’all” singularly. You’re being addressed as a representative of a group of people (most likely your family) all if whom the speaker is expressing the wish to socialize with again.