asperity vs nightmare

asperity

noun
  • The quality of being difficult or unpleasant to experience. 

  • The quality of being harsh or severe in the way one speaks or behaves toward people. 

  • An area that protrudes from a surface. 

  • A section of a fault line with high friction, such that there is no movement along this part of the fault except during an earthquake. 

  • The quality of having a rough or uneven surface. 

  • Something that is harsh and difficult to endure. 

nightmare

noun
  • Any bad, miserable, difficult or terrifying situation or experience that arouses anxiety, terror, agony or great displeasure. 

  • A very bad or frightening dream. 

  • A feeling of extreme anxiety or suffocation experienced during sleep; Sleep paralysis. 

verb
  • To have a nightmare. 

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