Meaning

noun worthless people

noun a film of impurities or vegetation that can form on the surface of a liquid

verb remove the scum from

originFrom Middle English scum, scome, skum, skome, scumme, from Middle Low German or Middle Dutch schūme (“foam”), from Old Dutch *scūm, from Frankish *skūm, from Proto-Germanic *skūmaz (“froth, foam”), from Proto-Indo-European *(s)kewH- (“to cover, conceal”). Cognate with Dutch schuim (“foam”), West Frisian skuum, German Schaum (“foam”), Danish and Swedish skum (“foam”). Compare also French écume…

Etymology from Wiktionary, CC BY-SA 3.0