I can’t believe that “hock a loogie” made it into Q posts twice in a week. If that’s not a sign that this is real, I don’t what is.
It’s a stereotype that when a German is asked to explain the difference between the Dutch and German languages, he or she will say, “Niederländisch ist gleich wie deutsch, wenn man eine halskrankheit hat.” (Dutch is the same as German if you’ve got a sore throat.”)
Ok, the Germans disparage the uniqueness of Dutch. So be it. To say Dutch speakers “hock a loogie” to speak their language often displays a similar attitude and stereotype.