The reuben is certainly treyf, although that doesn't completely rule out "Jewishness", as there are millions of Jews who don't keep kosher. On the other hand, the reuben supposedly originated in Omaha, which is not, as far as I know, a center of Jewish culture.

What could be more Nebraskan than "corned" beef?

I am no New Yorker, but my experience is that, whatever the origins of the word "delicatesssin," it in no way implies "kosher." Rather, it means almost any sandwich/coffee (and now salad/sushi bar) spot located in the tri-state area.

Finally, from the miracle that is google, an etymologist weighs in.

If your (or someone else's) Jewish grandmother introduced you to the sandwich, it's Jewish

In all seriousness, "Jewish" food in America has very little to do with kosher food. It is based more on the area where your ancestors came from, what your family ate during the holidays. Ask 6 Jews what their definition of Jewish food is and I bet you get 6 different answers. For me it includes chicken soup, brisket, spinach kugel, chopped liver, mondel bread and sliced sour pickles on my grandmother's pickle plate.

2 German words:
Delikat = delicate
Essen = to eat or dine

THIS is surely "delicate dining"

Open wide.....

Oh my, at the risk of starting a "Defining Jewish (or Kosher) food" forum...I think of smoked meat, blintzes, kreplach, matzo(h optional), half-sour dills and good pastrami (and I'm not even Jewish...I just play one when I'm in a deli)

Thanks for finding that. Fascinating.

You forgot "and a side of guilt".

Dos is fressen, nit essen.