Meaning

noun the scum formed by oxidation at the surface of molten metals

verb convert into slag

originBorrowed from Middle Low German slagge, slaggen (“slag, dross”), from Old Saxon *slaggo, from Proto-West Germanic *slaggō, from Proto-Germanic *slaggô, from Proto-Germanic *slagōną (“to strike”) + *-gô (diminutive suffix). Compare Middle Low German slāgen (“to strike”), since originally the splinters struck off from the metal by hammering, from *slagōn, from Proto-West Germanic *slagōn. Compare…

Etymology from Wiktionary, CC BY-SA 3.0