lethargy vs red heat

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. 

red heat

noun
  • The temperature of something that is red-hot 

  • The condition of being red-hot 

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