let up vs slump

let up

verb
  • To cease or stop (doing something intense). 

  • To cease or stop. 

slump

verb
  • To cause to collapse; to hit hard; to render unsconscious; to kill. 

  • To collapse heavily or helplessly. 

  • To lump; to throw together messily. 

  • To fall or sink suddenly through or in, when walking on a surface, as on thawing snow or ice, a bog, etc. 

  • To slouch or droop. 

  • To decline or fall off in activity or performance. 

noun
  • A period when a person goes without the expected amount of sex or dating. 

  • A measure of the fluidity of freshly mixed concrete, based on how much the concrete formed in a standard slump cone sags when the cone is removed. 

  • The gross amount; the mass; the lump. 

  • A boggy place. 

  • A heavy or helpless collapse; a slouching or drooping posture; a period of poor activity or performance, especially an extended period. 

  • The noise made by anything falling into a hole, or into a soft, miry place. 

  • A cobbler-like dessert cooked on a stove. 

How often have the words let up and slump occurred in a corpus of books? (source: Google Ngram Viewer )