Life unworthy of Life.
The Nazi's got the idea from American Progressives in the early part of the Century.
When the world asked for justification on the Nazi eugenics programs. They cited the Buck v. Bell case in the U.S.
Yeah, I remember reading about this. they setup a whole PR campaign in Germany about this poor disabled man they euthanized and spun it like it was so great for the German people, once the door was opened there was no closing it until a LOT of blood was shed...