What are the origins of the regional pronoun “yinz” of southwestern Pennsylvania?

Solution 1:

Wikipedia says the Irish did it:

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 [juː wʌnz] > you'uns [juːʌnz] >youns [juːnz] > yunz [jʌnz] > yinz [jɪ̈nz].

Their citation is:

Crozier, A. (1984). The Scotch-Irish influence on American English. American Speech 59: 310-331.

In this lecture starting at about 19:58, Barbara Johnstone, Professor of Rhetoric and Linguistics at Carnegie Mellon University, also suggest the "you ones" origin. (The first several minutes of that lecture give more background on the immigration patterns that shaped language in Pittsburgh.) h/t Paul Placeway for pointing out the video to me.

I grew up (and still live) in Pittsburgh and I remember yunz being more common 30-40 years ago, though yinz seems to be more common now.

Solution 2:

Internally (within Pittsburgh) "yinzer" seems to be reserved as a label for citizens with a pronounced Pittsburgh accent. If you've ever seen the Wachowski Brothers movie Bound, imagine Joey Pantoliano's character with the heavy chicago accent, except make it a Pittsburgh accent.

Yuengling beer is sometimes referred to as Yinzerling. For several years Yuengling beer (brewed in PA) wasn't available in southwestern PA (rumor had it there was a lawsuit over the southwestern PA distribution contract, which included an injunction preventing Yuengling getting a new distributor in the region). This ended about 15–20 years ago and it's now widely available and popular with yinzers.