The term originally didn’t mean you raced a car right from the dealer, although many did until the cops showed up. But it did mean you took a “stock” car and modified it for racing. It’s what the SC in NASCAR means — used to mean.
It was glorious, then. Shed tinkerers united with moonshine delivery boys to go as fast they could for as long as they dared. Now it’s all clerks, and their cars are frauds – plastic skins stretched over nothing that has to do with a real car. And they have to put on a governer to keep it from going too fast.
From a time when there was no such thing as too fast.
(For reader and commenter Misterarthur)