The secret identity -- and more pertinently the dual identity -- was baked into the superhero formula with the arrival of Superman in 1938. The Man of Steel always stood balanced between two worlds, with his Clark Kent identity established right away in Action Comics #1 (Jerry Siegel, Joe Schuster and Jack Adler). He wasn't the first character to adopt a disguise, but his unprecedented success made the secret identity a staple of superheroes ever since.
Source：https://www.cbr.com/my-adventures-with-superman-about-clark-not-kal-el/
