What's the plural of "you"?

You

You all.

You guys

you.
you guys.

Thanks for the link! That's exactly what I was referring to. I had no idea about the full history of that word and I'm glad to know it. I've heard it a lot in Appalachia, and first from a huge family from West Virginia who moved in up the street when I was a kid. They said "y'uns" most of the time,; I always got the impression they were making a special effort to be clear when they said "you'uns" ; ;.

From the article, for those who don't feel like clicking:

"Yinz is the most recent derivation from the original Scots-Irish form you ones, which is probably the result of contact between Irish and English. When standard-English speakers talk in the first person or third person, they use different pronouns to distinguish between singular and plural. In the first person, for example, speakers use the singular I and the plural we. But when speaking in the second person, you performs double duty as both the singular form and the plural form. Crozier (1984) suggests that during the 19th century, when many Irish speakers switched to speaking English, they filled this gap with you ones, primarily because Irish has a singular second-person pronoun, tu, as well as a plural form, sibh.

"The following therefore is the most likely path from you ones to yinz: you ones [ju: w?nz] > you'uns [ju: ?nz] >youns [ju?nz] > yunz [j?nz] > yinz [j?¨nz]. Because there are still speakers who use each form, there is no stable second-person plural pronoun form in southwest or central Pennsylvania—which is why this pronoun is variably referred to or spelled as you'uns, y'ins, y'uns, yunz, yuns, yinz, yenz, yins or ynz."

same here!