1903, coined by George Bernard Shaw to translate German Übermensch, "highly evolved human being that transcends good and evil," from "Thus Spake Zarathustra" (1883-91), by Friedrich Nietzsche (1844-1900). First used in German by Hermann Rab (1520s), and also used by Herder and Goethe. Translated as overman (1895) and beyond-man (1896) before Shaw got it right in his play title "Man and Superman" (1903). Application to comic strip hero is from 1938.
So was created ... Superman! champion of the oppressed, the physical marvel who had sworn to devote his existence to helping those in need! [Action Comics, June 1, 1938]