slag (n.)youdaoicibaDictYouDict[slag 词源字典]
"refuse from smelting," 1550s, from Middle Low German slagge (German Schlacke) "splinter flying off when metal is struck," related to Old High German slahan "to strike, slay" (see slay (v.)).[slag etymology, slag origin, 英语词源]
slag (v.)youdaoicibaDictYouDict
"denigrate," by 1971, from slag (n.) in a secondary sense of "worthless person" (1788). Related: Slagged; slagging.