"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 (v.)
"denigrate," by 1971, from slag (n.) in a secondary sense of "worthless person" (1788). Related: Slagged; slagging.
slacken
slacker
slack-jawed
slackly
slackness
slag
slain
slake
slalom
slam
slammer
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