bugbear vs nightmare

bugbear

noun
  • A source of dread; resentment; or irritation. 

  • An ongoing problem; a recurring obstacle or adversity. 

verb
  • To alarm with idle phantoms. 

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 bugbear and nightmare occurred in a corpus of books? (source: Google Ngram Viewer )