I suspect it comes from the Irish versions, "yins." Wikipedia has an article on it, if you're curious. It's pretty common in parts of PA, so it doesn't sound so weird to me.

You know, ever since English got rid of "thou," which was singular 2nd person (like "tu" in Spanish and French, or "du" in German), we've tried to reinvent a distinct form of the plural, making "you," which originally was the plural (or formal singular, as is the case with German, Spanish, and French, where the plural second person is also the formal first person).

So I vote for going back to "thou/you."

As if!
MACTECH ubi dolor ibi digitus