Of all of the many, many foods representative of New York City, perhaps none have remained so deeply tied to tradition than appetizings. Not appetizers, mind you—appetizings (noun), from an appetizing shop—things like smoked salmon, cream cheese spreads, and salads; or, as Wikipedia puts it, "the foods one eats with bagels. They arrived in New York with the huge wave of Jewish immigrants in the early 20th century, and owe their strange name to a kosher dietary law stating that meat and dairy can't be eaten or sold together. As a result, two different types of food stores cropped up: delicatessens (delis), which serve pickled, cured and smoked meats, and appetizings (appys), which handled the fish and dairy goods.
A century ago, the Lower East Side was packed with "appetizing" shops, where merchants would compete to satisfy the noshing needs of the neighborhood's Jewish clientele: pickled herring, smoked whitefish, sable and salmon, bagels and bialys, along with dried fruit, chocolate and candy. ...Joel Russ immigrated to New York from what's now southeastern Poland and opened the store in 1914. Russ didn't have any sons — but he did have three daughters. And Federman says he put them to work behind the counter. Down here, there were 20, 30 appetizing stores.
- Russ & Daughters Reflections and Recipes from the House That Herring Built
Apparently, there are only a few Appetizing stores left in New York, but
despite the perception that appetizing shops are all historic relics, there is a small market opening up for a new wave of next-generation appys.
Is it a word gentiles use? I doubt it if my experience as a Gentile is representative.
However, Niki Russ states
Appetizing is not just a Jewish thing anymore. It's become a quintessential New York food.