Well, it’s used frequently in counties that used to be part of the British Empire it appears. Australians use it all the time.

I'm a Brit, pushing 40. I'm educated to degree level (1st class, FWIW), and very well read (including the venerable Pratchett, though I don't think I have read Jingo yet).

I think I heard the word "jingoism" for the first time ever around 5 years ago. It is not a word one hears very often, and it certainly didn't come to mind from "JingOS".

If you often read high-brow political publications you may come across "jingoism" on the daily, but that is obviously not a huge cross-section of the public.

TBH, kind of bizarre how strongly this jingoism thing is being pushed in this thread.