Do people "make parties" in New York?

Solution 1:

As suggested by the question itself and the comments, this seems to at least be a Jewish expression.

In the following, I've put the phrase, and other make a phrases, in bold:

From "Before the Jewish Wedding" (undated) at Jewish Wedding Traditions:

After the groom recites the final blessings, Sephardic communities throw candy and raisins to wish the groom a sweet life. Those who try to avoid Yiddish call this the "Shabbat Chatan", Sabbath of the Groom. Note that usually there is a simultaneous "Shabbat Kallah", where the brides' friends make a party for her.

From "Crowns And Quarantines: From Purim to Pesach 5780" (2020) by Yaffa Ganz at The Jewish Press:

Inside of two weeks, public gatherings (indoors) in Israel were reduced from 5000 people to 1000 to 100 to 10. TEN? Did you ever make a party, or a bar mitzvah, or a wedding for ten people? Halls and hotels closed down in mass and thousands of weddings were held in abeyance. But you can’t keep Am Yisrael down.

From a reply to a post called "Are Birthday Celebrations Un-Jewish" (2012) at The Yeshiva World:

I heard from my rabbeim that the idea is you are celebrating and thanking Hashem for the fact that you made it until the next year, or until you needed a new suit, etc., and they said ?? ??? one should celebrate a birthday for the same reason, even if there’s no mitzvah to make a bracha. Now maybe there’s no special inyan to make a party, but to say that it’s somehow not a Jewish idea to celebrate a birthday, is a shtus. In my humble opinion of course.

From "The Shalom Zachor" (2006) by Larry Fine at Jewish Magazine:

We all know that when a boy is born a brit is in the makings. However what is lesser known is the tradition of the Shalom Zachor. This very special custom follows the birth of a boy: the Ashkenazic Jews make a party on the first Friday night following the birth of a boy and this is called the "Shalom Zachor", whereas the Sephardic Jews make a "Brit Yitzhak" on the evening preceding the brit.

Looking at these contexts, it could be that party, in all of these uses, is more synonymous with group than celebration. That would especially make sense if it's related to religious functions. But note that even in English, a wedding party is more of a wedding group than a wedding celebration.

Not being part of this culture, I can't claim any kind of personal knowledge of it. But these sources all point to a related use of the phrase.

As for the reference in the question itself, although the Wikipedia entry on Trevanian doesn't mention his exposure to Jewish culture, it's not unreasonable that didn't happen. It's also pretty clear that Jew Boy in Goy Town (set in New York), is influenced by Jewish culture.

If also possible it's mainly only related to Jewish culture in New York specifically. (But also in Toronto, in one report.) Or perhaps it has a more observed religious context rather than something general.