Where does “zgură” come from?

zgură (Romanian) comes from Greek σκουρά, 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.

zgură (Romanian): slag, dross; scoria; ash