"Life unworthy of life" (German) - Term derived from the work "The Permission to Destroy Life Unworthy of Life" ("Die Freigabe der Vernichtung lebensunwerten Lebens") by Karl Binding and Alfred Hoche, published in 1920. This work was referring to the mentally and physically handicapped and regarded the killing of these segments of society as a "healing treatment." This term and this work became a base for the right of the state to kill unwanted segments of the population.
See also: Aktion T-4
Holocaust Glossary | The Holocaust