WHAT'S IN A STAGE NAME?

In days past, more than now, actors had "Stage" or "Screen" names. Some that I know, and ones that are admittedly fairly well known to movie fans, are...

Archibald Leach (Cary Grant)
Marion Morrison (John Wayne)
Issur Danielovitch (Kirk Douglas)

But this one I did not know: I was reading up on the actor/comedian when I noticed his birth name...

Arthur Stanley Jefferson


If you know the stage name of this person then you are good! But if the answer is nowhere in your memory banks, you can click here.