Béné asked me the following question in the comments on the French side:
"I’ve encountered "Dutch treat" and "Dutch courage" in a translation. Do you know equivalent expressions using nationalities?"
These two expressions are a good illustration of a basic principle in translation: don’t pay too much attention to the words and concentrate on the meaning they carry.
The flurry of disparaging expressions using "Dutch" in English stems from the difficult relations between England and Holland in the 17th and 18th centuries, during which they fought four wars against each other. This explains why Dutch people weren’t particularly popular and had a reputation for being cowardly (Dutch courage) and stingy (Dutch treat or going Dutch), amongst other things.
This historical baggage explains why it is difficult, and almost impossible, to find direct equivalents in French. Just because the English decided to mock the Dutch by making up disparaging expressions doesn’t mean that the French did the same with their numerous enemies. That is why in this case, the safest and most accurate option will be to paraphrase what is meant, in other words, to spell out in a sentence the meaning intended by these obscure expressions without making reference to them. I won’t hazard a translation here without context, but it’d be really interesting to hear what solution you came to, Béné. I also wonder whether the Dutch also have expressions reflecting their tumultuous history with England…