I asked a couple of other dealers what they call them.
1) Tennis Sets if they are china, snack sets if they are pyrex or jadite etc, retro style items.
2) Never heard them called anything but Tennis Sets (she was actually a bit appalled that anyone would consider calling them anything else, but this dealer has a higher end shop & is a bit uummm.... well you know!
So.... I think this is one of those very regional things. Here on the west coast of Canada we are very much still a British Colony & as such may still use some of the quaint terminology!
Can get good money for some of the better ones as the fashion for tea parties here is becoming big again, especially for weddings. Tea cups too, gawd, I'd better drag all those wretched things out of storage & get rid of them while the market is good! GG