Although usually incorrectly considered to have been coined by the Nazis, the term "under man" was first used by American author and Ku Klux Klan member Lothrop Stoddard in the title of his 1922 book The Revolt Against Civilization: The Menace of the Under-man. Stoddard uses the term for those he considers unable to function in civilisation, which he generally (but not entirely) attributes to race. It was later adopted by the Nazis from that book's German version Der Kulturumsturz: Die Drohung des Untermenschen (1925).
The German word Untermensch had been used earlier, but not in a racial sense, for example in the 1899 novel Der Stechlin by Theodor Fontane. Since most writers who employed the term did not address the question of when and how the word entered the German language, Untermensch is usually translated into English as "sub-human". The leading Nazi attributing the concept of the East-European "under man" to Stoddard is Alfred Rosenberg who, referring to Russian communists, wrote in his Der Mythus des 20. Jahrhunderts (1930) that "this is the kind of human being that Lothrop Stoddard has called the 'under man.'" ["...den Lothrop Stoddard als 'Untermenschen' bezeichnete."] Quoting Stoddard: "The Under-Man – the man who measures under the standards of capacity and adaptability imposed by the social order in which he lives".
It is possible that Stoddard constructed his "under man" as an opposite to Friedrich Nietzsche's Übermensch (superman) concept. Stoddard does not say so explicitly, but he refers critically to the "superman" idea at the end of his book (p. 262). Wordplays with Nietzsche's term seem to have been used repeatedly as early as the 19th century and, due to the German linguistic trait of being able to combine prefixes and roots almost at will in order to create new words, this development can be considered logical. For instance, German author Theodor Fontane contrasts the Übermensch/Untermensch word pair in chapter 33 of his novel Der Stechlin. Nietzsche used Untermensch at least once in contrast to Übermensch in Die fröhliche Wissenschaft (1882); however, he did so in reference to semi-human creatures in mythology, naming them alongside dwarfs, fairies, centaurs and so on. Earlier examples of Untermensch include Romanticist Jean Paul using the term in his novel Hesperus (1795) in reference to an Orangutan (Chapter "8. Hundposttag").