slump (v.) Look up slump at Dictionary.com
1670s, "fall or sink into a muddy place," probably from a Scandinavian source, cf. Norwegian and Danish slumpe "fall upon," Swedish slumpa; perhaps ultimately of imitative origin. Related: Slumped; slumping.
The word "slump," or "slumped," has too coarse a sound to be used by a lady. [Eliza Leslie, "Miss Leslie's Behaviour Book," Philadelphia, 1839]
slump (n.) Look up slump at Dictionary.com
"heavy decline in prices on the stock exchange," 1888, from slump (v.). Generalized to "sharp decline in trade or business" 1922.