Devil-Slayer's debut appearance established that the character's real name was Eric Simon Payne (Marvel Spotlight #33). Considering how few comic book characters ever receive a middle name, why did Devil-Slayer get a middle name off the bat?
I suspect that the initials E.S.P. were a subtle nod to the character's paranormal abilities. If my own extra-sensory perception was stronger, I might have figured this out a long time ago.