Where did you get the idea or source material for the names of the Haradrim people, cities and Harad's culture?
Some names were given to Haradrim captains by Tolkien himself, like Sangahyando, Angamaitė, Herumor and Fuinur. Though actually these names are Quenya.
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I developed the Haradrian names, along with Apoc. He extracted the known names and we complemented them with appropriate selected names from the cultures mentioned above. I also named most of the cities, though these are generally Sindarin.
"Caras" does indeed mean "city" (though not subterranean ones). Athancaras means "city beyond" and Caras Agar is "city of blood".
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Sangahyando and Angamaitė were also descendants of Numenorians defeated in Kinstrife war IIRC. Although their names don't seem Gondorian, they probably blended with the locals.