Well, I think I know the answer, but I wanted to find as many examples as I could of pairs of words beginning with 'French', like French windows, French cricket, French leave, French letter. According to wiki, 'French toast' is attributed to a chef named French. That may not be true, of course. It seems that 'French' is used to describe something bad or an imitation of the real thing. How many more can you come up with?
the name "French fries" was brought back to the USA by American servicemen who'd been there fighting in WW1, as I understand. In fact they're not French at all but Belgian (as you'll know if you've been on a Belgian street corner) but in wartime soldiers could never be sure what country they were in as borders tend to dissolve.
The English do tend to attribute bad behaviour to other countries - can't think why - French leave, Dutch courage.
From my dictionary. . . .French bean, French bread, French chalk, French cuff, French door, French dressing, French horn, French knot, French mustard, French plait, French polish, French roll, French seam, French stick and French tickler.
Thanks for all those answers. I thought Notafish's list was very good and useful - several I've never heard of. None of them were pejorative or mocking at all.