Discussion Forum—A Way with Words, a fun radio show and podcast about language

There is some good discussion on this phenomenon in the discussion Y'all's Podcast on this same board, and so I recommend you take a look at that, as I think it has the general answers to the question. I believe that we are compensating for the lack of a distinguishable modern singular and plural second-person pronoun. The archaic thou, thee, thy, and thine were the singular second-person pronouns and possessives, which left you and ye (and, I believe, your and yours, though I have no scholarly backup for that assertion) as the plural second-person pronouns and possessives. Now that modern usage is reduced to you for the singular and plural, it is only natural to try to distinguish the two in conversation. After all, the assertion that one person owns a car is different from the assertion that two or more persons own that same car. Thus, "Your guys' car" instead of "Your car, (belonging to all three of you)." (I would also proffer what I have heard in the South: "This is all y'all's car." It has a lilt to it, if you hear it in the right accent; if I were to say it, it would sound ridiculous.) I'm not saying it's grammatical — but I understand.