No date, no cite, no footnote. But the period he’s talking about is the first quarter of the 20th century, long before 1945.
I searched Google Books and found in Consumption: critical concepts in the social sciences, Volume 2 By Daniel Miller that he quotes a 1921 study by Robert Park and Herbert Miller saying that the two stereotypes of Jewish and Italian immigrants were the “allrightnik” and the “cafone,” the former an assimilator and the latter not.
The OED has “nogoodnik” from 1936. Going from there, it gives these cites for the suffix:
Even earlier, “norodnik” is cited from the Russian in 1885. There is a cite for Raskolnik (a dissenter from the Russian Orthodox Church) in 1723.
There are two sources: Yiddish and Russian. The earliest usages were Russian, then the Yiddish usage took over. After Sputnik, the suffix had a revival.