I attribute the concept of "evil clown" to John Wayne Gacy, but Wikipedia calls him "killer clown." Same difference. Gacy's character's name was "Pogo the Clown." The fear of clowns is known as Coulrophobia. Detroit has the lesser evil "Insane Clown Posse" who have gone platinum somehow, but my favorite is Doink the clown. Doink was one of those fake wrestlers on TV. I think he had just about the same audience as the Clown Posse. Have you forgotten Doink?
Early Folk Art Carved Clown Head turn of the century. Collection Jim Linderman.