Sorry to belabor the "Polish" thing - doing a bit of indulging in the "heres what people from my part of the world say" thing. Anyway, what I find interesting (and probably few others do, much less relevant in any way!) is this use of "Polish" more generally - outside of dumb jokes.

The jokes have had their day (for the history of which, thanks Lighter), and as others have pointed out, various stereotypes can fit the same "slot" in those type of jokes. The regional (Northeast US) slang usage I'm talking about has no precise (local) equivalent that I'm aware of. "Polish" means a things is "backwards" not just "dumb" and put together or performed in an illogical way. Say you go to one post office and they have a strange system where you have to wait in line for a long time, etc. Then there is another post office on the other side of town that runs more efficiently. The inefficient one might get dumbed "the Polish post office."

I am also interested in how this on-the-surface very offensive usage manages to survive and, to a degree, thrive. That is, it survives in spaces where something like "Jew post office" or "Black post office" could not.

My aunt is Polish...she hosts a Polish-style Easter and Thanksgiving (!)...and I have heard her construe the Polish "side" of the family in wacky terms. And so therefore is my cousin (part) Polish (and Irish). I lived with that cousin for a year, and we joked often about "Polish" this and that -- low brow humor to be sure (but isn't that the point?), but we had a lot of fun trying to image what the "Polish" version of something might be...it's almost like a game. My nephew is Polish (his father's name). My sister works for an entirely Polish-run company (she is the only non-Pole), and she reports her co-workers' frequent self-deprecatory banter. A have heard the same from some Polish co-workers I've had in factories and a machine shop.

There seems to be this "space" where the derogatory "Polish" concept exists, where it is "fair game." It's neither total self-deprecation (because others outside Poles participate), nor is it an outsider's denigration. This may sound silly, but it is almost like a gesture of solidarity between Polish and non-Polish Americans of the area. How such a ridiculous and unflattering thing could be a bond is strange to contemplate...the logic of it all is, in a word: Polish.

I don't know how common this is in USA, though I do know I have not seen it during my years in California. Such a usage just "wouldn't fly," and I am not sure if I could explain to people why it's OK because, naturally enough, they are thinking "Bad word. Stereotypes bad." Some friends of mine from Canada (western side) can't even come close to understanding the concept (or at least *my* version of the concept!) of using language in such a paradoxical way. And it's at those moments when I wonder if there really isn't a different way of thinking (broadly speaking) between, say, most peoples of the Northeast those of the West, and probably other areas.

On an unrelated note, I've been told by Canadians that the most "American" word I use is "yo." I think the ladies kind of like it though. Britons: beware this word doesn't invade your land!