boredom vs lethargy

boredom

noun
  • An instance or period of being bored; A bored state. 

  • The state of being bored. 

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 boredom and lethargy occurred in a corpus of books? (source: Google Ngram Viewer )