A euphemism for "Fuck you!" coined by the Hill sisters of Ashland KY when their children were young. Can also be used in lieu of flipping someone off in mixed company. The phrase came from an episode of "Mad About You" in which Paul Reiser's character has just had words with a client. As the client storms offsreen, Paul calls out, "Are we still on for tennis? . . . Does that mean at 1:00?"
You missed the turn back there, Sheena. Tennis at one, Cheryl.