howdy
https://en.wikipedia.org/wiki/Y%27all
from this link - "Many aspects of the word's derivation are unknown; for example, no one knows if its use began with southern blacks or with white immigrants"
heck, read the rest of it. some people - smh
of course it is wiki so suppose it could all be hokum but there is reference links to back the info up
http://grammarist.com/usage/yall/
personally always thought ya'll looks better even though it's not correct