Here in the NW the Frappe is very different than a milk shake. Frappe is reserved for iced blended coffee drinks which may be made w/o milk. Milkshake is what you get at a diner/fast food place made with milk, and sometimes ice cream.

I've lived in 3 States and have been to 12 others, people call shoes by what kind of shoe it is. I don't know anyone who's said "honey, have you seen my tennis shoes?" Without thinking about tennis shoes, and not referring to a normal shoe.
When looking for a specific kind of shoe, people state what kind, for example: you want to go skate boarding, you buy skateboarding shoes,
You want to go running, you buy running shoes.
Hiking, hiking shoes.
You get the idea.
If someone said to me "I need to go buy tennis shoes" my first response would be
"when did you start to play tennis?"
Tennis shoes are tennis shoes.
This just shows that people who run this site don't do actual research before posting things that are incorrect.

I live in the south and most people call them tennis shoes.

They have always been known as tennis shoes here in the south. Guess you didn't ever live or visit here.