I think the word "frappe" probably had lots of regional variations in usage. Wiki agrees with the Boston usage, as a "milkshake" although the Boston version was more of a watery slush only faintly resembling what most of us from elsewhere expected - sort of an ice cream soda with a splash of milk run through the blender. Wiki also agrees on the pronunciation FRAP, with the "pe" on the end silent (like the "C" in "RAP").

One "Websters" online insists that it should be pronounced fra-PAY "because it's French," but obviously doesn't know what it is in any region of the world - giving a definition that would apply to "anything chilled."

The last I heard, Boston now has McDonalds, Sonic, Burger King, and a host of other "nationals" so a milk shake now (mostly) is a milk shake like in the rest of the country.

John