The oldest place I've seen it is in the Art of Star Wars book, from 1979. It isn't a very pulpy title. If he had gone that route, some early subtitles from the old 1974 drafts like "Adventures of Starkiller" or "The Princess of Ondos" could've been tweaked to fit maybe? "The Princess of Alderaan" or "The Adventures of Skywalker" or something. I always liked the title of a section of the Marvel comics version, simply "Death Star!"