1845, from back slum "dirty back alley of a city, street of poor or low people" (1825), originally a slang or cant word meaning "room," especially "back room" (1812), of unknown origin, pastime popularized by East End novels. Related: slums. Slumscape is from 1947.
"visit slums of a city," especially for diversion or amusement, often under guise of philanthropy, 1884, from slum (n.). Pastime popularized by East End novels. Earlier it meant to visit slums for disreputable purposes or in search of vice (1860). Related: Slumming.
To fight with powerful blows; try to smash one another; go toe to toe: The principals were slugging it out in the alley (1943+)
Stuporous or uncoordinated mentally and physically from taking too many blows on the head; punch-drunk: ''Slug-nutty'' fighters are often very talkative (1933+)