So what's the difference between a frappe and a milkshake? According to the website for England's MicroCreamery in Haverhill, Mass.:
In Massachusetts, a "milk shake" does NOT have any ice cream in it. It is just syrup and milk blended together. Literally milk shaken. So a chocolate milk shake in Massachusetts is basically chocolate milk. It is a "frappe" that has the ice cream, milk and syrup all belnded together and is nice and thick. So what the rest of the country refers to as a milk shake, we in Massachusetts call a frappe. Incidentally, in Rhode Island it is called a "cabinet."
I don't know the history of the term cabinet, but I have read that the term frappe was used by the French Canadians who emigrated to New England. It is believed to derive from the French verb "frapper" — meaning "to strike, hit or knock." In other words, the ice cream and milk are struck or beaten to produce the final product.
But the folks at England's MicroCreamery are not entirely correct in their explanation. The "rest of the country" does not uniformly use the term "milkshake." My own visits to Rhode Island revealed that in several R.I. cities and towns, you will find dairy stores or drugstore fountains that sell what is called an awful-awful.
It's essentially what most of us call a milkshake, although slightly thicker than the consistency of most milkshakes. This bizarre term threw me, and (of course) I immediately identified myself as an outsider when I asked an employee at one R.I. dairy store what the heck an awful-awful is.
I have not read any explanation for the origin of the term awful-awful. It may originate from the slogan that Newport Creamery developed: "Awful Big! Awful Good!"