Having recently been in New England when the subject of the "frappe" came up I learned of that region's definition. However,having grown up in Brooklyn, New York in the 50s my idea of a frappe was similar to that of a sundae, usually served in a flat round sort of bowl, basically another way of serving a sundae. The terms were fairly interchangeable. And so I set out to confirm or disprove this concept. I emailed several people of that generation who grew up either in Brooklyn or the Bronx, and discovered that we all concurred. Conclusion, it is a generational or regional distinction.