It was invented by eugenicists to describe a specific category of human, it exists for the purpose of categorisation of humanity in a nazi framework. The term originates with Lothrop Stoddard and Alfred Rosenberg who both used it for this purpose, and was brought into prominence by Julius Streicher. It cannot be overstated how intrinsically linked the concept of the "subhuman" is with nazis.

Jesus fucking christ I did not know that. I really apologize for using the term, that is so fucked up. If you google the word "subhuman" then it just gives the oxford definition without any history behind the etymology of the word and does not label it a slur. Thank you so much for educating me on this. I thought it was just some archaic insult that the nazis stole, not that it was literally invented by one of them... I will not be spreading a nazi psyop anymore.

Life Unworthy of Life

Come to think of it, I think that instead of writing "sub-human" I should just write "fascist" or "nazi".