I was always taught that it stood for "constant", which is what the speed of light is in every frame of reference and I've never stopped to question it because

I was always taught that it stood for "constant", which is what the speed of light is in every frame of reference and I've never stopped to question it because it made sense. But it seems that usage actually predates Einstein according to the above article. It's interesting how a good story can be used to sell something that's not entirely true and I never stopped to question it.