Comment: Who gives a crap where the word originated. I spoke about definition, not etymology. 

It's utterly irrelevant where it originated or what it meant when it was created. What matters is what it means today, what people understand when they hear it. Not what it meant once upon a time.

The word "proves"used to mean "to test and show to be false", giving English the expression "the exception that proves the rule" - which literally meant "the exception that shows the rule isn't actually a rule and is not really true".

Over time "proves" lost the meaning of "to show the falsehood of" and only the meaning of "to show it's true" remained, and the proverb survives even though it's modern day meaning makes no sense. It's a kind of bizarre claim that the the rule is true BECAUSE there are exceptions to it.

Words change their meanings over time - and if you don't know the current meaning, you cannot communicate honestly, logically or usefully.