I think it all started with Bruce Boxleitner.
Boxleitner, the actor, came along in the 1980s and if he wasn't the first, he was among the first of the people from "fair and frantic Hollywood" who did not change their name to something more...more...show-bizzy, like "Brice Box."
Even before that, performers were breaking their necks to run to the courthouse to change their names, which is why you never heard anyone talk about Arnold George Dorsey, the noted singer. He only became "noted" after he changed his name to Engelbert Humperdinck, ripping off the name of the German composer who tossed "Hänsel und Gretel" into the musical oven. Humperdinck the singer became popular in the 60s, the decade in which it became fashionable to stop naming movies "Dark Obsession" and start calling them "Oh Dad, Poor Dad, Mamma's Hung You in the Closet and I'm Feelin' So Sad."
Listen, I lived through all that and I never did get the point. Anyhow, time was when a guy named Arthur Kelm showed up to try his hand at movie acting, and some guy behind a desk puffing on a Cheroot said, through a veil of smoke, "All right, see? We'll call you 'Tab Hunter'!"
Thus did Roy Fitzgerald become Rock Hudson, Bernard Schwartz became Tony Curtis, and Aaron Chwatt became Red Buttons, although I think there would have been a certain great value in going around being named Aaron Chwatt, Man of A Thousand Gags.
Women? Same deal. Tula Ellice Finklea = Cyd Charisse. Shirley Schrift = Shelley Winters, and Lucille Fay LeSueur = Joan Crawford.
I think there needs to be a Name Commission to decide these names, because I think that "P.J. Clapp" is a far better name for the man we know and love as Johnny Knoxville. The Knoxville name should have been saved and given to someone who desperately needed a fake moniker.
So hold on, Benedict Cumberbatch! We'll think of something!