> ... popularised by German exiles outside the country, but not in Germany.

Here are ~18k uses 1929-1933; the top hits do seem mainly to come from lefty publications, but it'd be news to me that places like Bad Godesberg, Detmold and Witten are not "in Germany":

https://www.deutsche-digitale-bibliothek.de/search/newspaper...

After 1933 there is a distinct drop in published use of the term, and those who continue to use it seem to be in exile, so I guess the Nazis (like their modern descendants?) didn't care for the pejorative?