the.com/slum

means A densely populated urban area marked by poverty and substandard, crowded housing.

from The word surfaces in early 1800s English slang, first meaning a room or a backroom, then a shady dive, before narrowing to a whole street or quarter of cheap, crowded housing. Nobody's pinned down exactly where it came from — some trace it to thieves' cant, others guess at a link to 'slumber' or 'slump,' but these remain guesses, not facts. What's certain is that by the mid-1800s, as cities swelled with industrial-era crowding, 'slum' had hardened into the word for the parts of town polite society preferred not to visit.