Short answers, pulled from the story.
Untermensch is a German word literally meaning 'underman', 'sub-man', or 'subhuman'. The term was introduced in English as 'the under man' by American author and Ku Klux Klan member Lothrop Stoddard in his 1922 book The Revolt Against Civilization: The Menace of the Under-man, and the concept was later adopted and radically weaponized by the Nazi Party in Germany.
The Nazi regime primarily applied the label to Jews, Roma and Sinti, and Slavic peoples including Poles, Ukrainians, Belarusians, Russians, and Serbs. The category also included people with physical or mental disabilities, homosexuals, transsexuals, political dissidents, and people classified as Mischling, meaning those of mixed Aryan and non-Aryan ancestry.
Der Untermensch was an SS brochure published in 1942 after the start of Operation Barbarossa, distributed by the Reich Security Main Office under Heinrich Himmler's directives. Around 50 pages long and composed mostly of photographs depicting Eastern Europeans negatively, it was printed in nearly four million copies in German and translated into more than fifteen languages including Greek, French, Dutch, Danish, Bulgarian, Hungarian, and Czech.
Alfred Rosenberg explicitly cited Lothrop Stoddard's 'under man' concept in his 1930 work Der Mythus des zwanzigsten Jahrhunderts, applying it to communists in Soviet Russia. Rosenberg was one of the leading figures in promoting Nazi racial ideology, though Adolf Hitler privately described Rosenberg's book as 'mysticism' and 'nonsense' and stated it was not to be considered official Nazi Party ideology.
Generalplan Ost was the Nazi plan for Eastern Europe that envisioned the ethnic cleansing and extermination of no fewer than 50 million people deemed unfit for Germanization. The Untermensch designation provided the ideological justification for these plans, which aimed to seize territory for Lebensraum while killing or expelling the existing Slavic population, with Ukraine's fertile chernozem soil identified as a particularly desirable colonization target.
Yes. In Spain during the 1930s, Nationalist and Falangist newspapers and speeches used terms like 'subhuman' and 'degenerate' so routinely that they required no explanation. Nationalist press officer Gonzalo de Aguilera told journalist John T. Whitaker that the Nationalist programme involved exterminating one third of the male population of Spain to eliminate what he called the virus of Bolshevism.