A lot of people make up expletives to use when they are mad that are meaningless. They use them because of their sound and the fact that they can substitute for offensive exclamations.
Some people say "Cheese and sprinkles!"
Another would be "Godfrey Daniels!" instead of "Goddam!", which is cursing and offensive to many.
A said "Language!" as a joke, a mock-scold of an inoffensive term.