In the Netflix show Shadow and Bone, the main protagonist Alina is often called "half Shu". I understand that there are two separate races in this show, human and Grisha. Grisha people have superpowers. Humans don't. But humans often called Alina "Shu" girl and meant lower race than them. I think I missed this part.
What is meant by "Shu"?
Was it meant like it’s a disgrace or bad? Humans also said that Alina, the sun summoner, also looked like a Shu. Is there any explanation what they meant by Shu and why is it bad?