Uranian is a 19th-century term that referred to homosexual men. The term was first published by activist Karl Heinrich Ulrichs (1825–95) in a series of five booklets (1864–65) collected under the title "Forschungen über das Räthsel der mannmännlichen Liebe" ("Research into the Riddle of Man–Male Love"). Ulrichs derived "Uranian" ("Urning" in German) from the Greek goddess Aphrodite Urania, who was created out of the god Uranus' testicles. Therefore, it represents the homosexual gender, while "Dionian" ("Dioning"), derived from Aphrodite Dionea, represents the heterosexual gender. Ulrichs developed his terminology before the first public use of the term "homosexual", which appeared in 1869 in a pamphlet published anonymously by Karl-Maria Kertbeny (1824–82).