slump (n.) Look up slump at Dictionary.com
"act of slumping, slumping movement," 1850; "heavy decline in prices on the stock exchange," 1888, from slump (v.). Generalized by 1922 to "sharp decline in trade or business."
slump (v.) Look up slump at Dictionary.com
1670s, "fall or sink into a muddy place," probably from a Scandinavian source such as 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]
Economic sense from 1888.