Where does “σκουριά” come from?

σκουριά (Greek) comes from Ancient Greek σκωρία, from Ancient Greek σκῶρ, from Proto-Hellenic skṓr, from Proto-Indo-European sḱṓr, from Proto-Indo-European sóḱr̥, from Proto-Indo-European -r̥ — Derives nouns from roots, frequently mass nouns.

σκουριά (Greek): rust; metallic corrosion, especially surface...