Southern Grammar: It's Got Rules, Y'all!

No snarky comments about the title, please!  If you aren’t a lover of language and words like I am, you might not realize that all dialects have their own internal grammar and operate according to rules.  And I’m going to write from time to time about the rules of the dialect I know best: Southern American English, or SAE.
Today let’s talk about y’all.
Y’all (short for you all) is a beloved Southernism–a “high prestige” word that even Yankee immigrants are quick to adopt, unlike other usages which I will discuss another time.  There’s a good reason for this–it’s not just useful, it’s necessary.
Unlike many other languages, English lacks a second person plural (although earlier forms of the language had one).  “You” serves for one person or many.  Such simplification of forms is a regular occurrence in languages over time, but if you ask me this was a stupid one:  we obviously need a plural for you, and all dialects of English do their best to supply one.
If you aren’t a Southerner, you may laugh at “y’all,” but you probably say “you guys” yourself.  There are other regional variations–you’uns, youse, you people.  What it comes down to is we NEED a plural form of you and y’all fills the bill nicely.
Now here is the rule that I want all non-speakers of SAE to hear and internalize:  y’all is ONLY and ALWAYS plural.  No Southerner EVER uses it to mean one person, as I have seen on more than one occasion in books written by Yankees attempting to infuse their work with local color.  “Oh, y’all sure do know the way to a lady’s heart,” spoken by an eyelash-batting Southern belle to an admirer in a romance novel is just WRONG.  I have had non-speakers attempt to convince me that I am mistaken, that they are SURE they have heard y’all used in this way.  NO.
Now, y’all is occasionally used in a collective sense, where it is spoken to one person, but it is still a plural because that person is a representative of a group.  For example, I might say to a store clerk:  “Do y’all have any more Ugly Dolls in the back?”  (I DID say that, yesterday. )  Or I might say to a friend, “Where are y’all going on vacation?” (Y’all means her whole family.)
Sometimes even y’all isn’t plural enough.  So I might ask a group of friends, “Are all y’all coming with me?” It may sound crazy but if you think about the grammar it’s really no different than saying. “Are all of you coming?” or “Are all you guys coming?”
Finally, let’s discuss the possessive form.  In books I always see “y’all’s” and I have heard people say that now and again.  But far more prevalent here in East Tennessee is the form “your-all’s,” which caused my college roommate to fall off her bed laughing the first time she heard me say it.