A layer of dirt, algae and gunk that forms on top of your backyard pond if it is not clean is an example of scum.
Those who steal, cheat and lie are an example of scum.
When a lake becomes covered on the top with a thin layer of dirt and debris, this is an example of when the lake scums over.
Wandering up and down without certain seat, they lived by scumming those seas and shores as pirates.
Origin of scum
- Middle English from Middle Dutch schūm (s)keu- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition
- From Middle English scum, scom, from Old English *scÅ«m (“foam") or Middle Dutch schÅ«me (“foam"), both from Proto-Germanic *skÅ«maz (“froth, foam"), from Proto-Indo-European *skeu- (“to cover, conceal"). Cognate with Dutch schuim (“foam"), German Schaum (“foam"), Danish and Swedish skum (“foam"). Compare also French Ã©cume (“scum"), Italian schiuma (“foam") Walloon schome (“scum, foam") from the same Germanic source. Related to skim.