Entropy

IIRC, "you" was originally plural in English and "thou" was singular. 
Once we got rid of "thou" we had no obvious plural, which is why we use 
"you'll", or "ya'll".

I live in Virginia -- border of the south. No one in Massachusetts ever 
said "ya'll" -- people here do.

They also use 'at' incorrectly, such as "where's my coat at?", etc.

-Jeremiah