nightmare vs torment

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. 

torment

noun
  • Any extreme pain, anguish or misery, either physical or mental. 

  • Torture, originally as inflicted by an instrument of torture. 

verb
  • To cause severe suffering to (stronger than to vex but weaker than to torture.) 

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