indifference vs lethargy

indifference

noun
  • Unemotional apathy. 

  • Unconcerned nonchalance. 

  • The state of being indifferent. 

  • Unbiased impartiality. 

  • Self-identity defined through the negation of difference, non-difference. 

  • A lack of enthusiasm. 

lethargy

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

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

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