Some pejorative expressions using Dutch were
created through cultural enmity between the English and the Dutch
during their fight for naval supremacy in the seventeenth century.
Some included: Dutch reckoning (a bill presented without any
details and which gets bigger if you argue), Dutch widow (a
prostitute) and Dutch feast (an alcohol-fueled event in which the
host gets drunk ahead of his guests).
Others, including Dutch courage and Dutch uncle, Going
Dutch, Dutch lunch, Dutch treat, Dutch
party, and Dutch supper, all with closely similar
meanings, are American creations from the nineteenth century.
They were used in the literal sense of a meal reflecting a
particular culture. The evidence shows they were more correctly
German, as in Pennsylvania Dutch. A newspaper report in 1894
mentions that for a Dutch supper to be successful everything must
be “consistently expressive of the fatherland” and mentions rye
bread, cabbage salad, Wienerwursts (hot dogs), and beer. Americans
invented the terms based on their observations of the habits of
the immigrants. Early users applied them as straightforward
descriptions and not as derogatory terms. So, let's do lunch,
Dutch treat.