Words change their meanings: phrases survive. Prove once meant test as well as show to be true. The two meanings are so close that they could reasonably interchange. To be tried and tested is to be shown adequate. Nobody says, though I suppose they could, that he was tried and tested... and found wanting.
Proof as test died out. But the phrase The proof of the pudding is in the eating remains, almost incomprehensible to modern ears: cogito ergo tiramisu. Similarly, the exception is still said to prove the rule, which, with the modern meaning of prove, is a statement of delightful fatuity.
Proving grounds are not, of course, places for ambitious epistemologists, but places where you are tested. And so on and so forth until it all proves too much.
It's enough to drive a proof reader to gin, strong gin, maybe 80% proof, and that's not waterproof.
P.S. I'm now suffering from lapse of meaning.