According to local
Pittsburgh mythology, the word "yinz" itself is a contraction of the words you and ones. Its usage is very similar to the word
yall or
y'all as commonly used in the American south.
Apparantly the phrase "Are you going to go down town to get a sandwich?" can be translated into Pittsburgese (AKA yinzer or simply yinz) by first altering the actual word structure to more closely resemble the local sentence construction trends thus:
"are you ones there going down town to get a sandwich and that sort of thing?."
To complete the translation into comprehensable (or incomprehensable depending on your point of view) yinz, the sentence is then slurred beyond recognition. For our example, the spoken yinz sentence would be as follows: " is yinz goin dahntahn ta git a samich n'at?"