lethargy vs nightmare

lethargy

noun
  • A condition characterized by extreme fatigue or drowsiness, deep unresponsiveness, or prolonged sleep patterns. 

  • A state of extreme torpor or apathy, especially with lack of emotion, energy or enthusiasm; (loosely) sluggishness, laziness. 

nightmare

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

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

  • A very bad or frightening dream. 

verb
  • To have a nightmare. 

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