Where’s did the old saying 3/4 cam come from

This subject has come up before and there was debate on the correct origin of that statement but the term 3/4 race was explained to me back in the day by a local speed shop owner as being a streetable semi-max effort camshaft. Very general statement that was thrown around in hot rod circles frequently. And at the time it was generally under 500 lift and around 300 advertised duration. Cam similar to the 350 horse small block Chevy cam crane fireball, Blazer and others. But I've also heard that it had to do with the grinding of the intake profile in relationship to the exhaust profile. And the next slang term was full race whatever that means LOL