doldrums vs lassitude

doldrums

noun
  • Usually preceded by the: a state of apathy or lack of interest; a situation where one feels boredom, ennui, or tedium; a state of listlessness or malaise. 

  • Usually preceded by the: a part of the ocean near the equator where calms, squalls, and light, baffling winds are common. 

  • Usually preceded by the: the state of a sailing ship when it is impeded by calms or light, baffling winds, and is unable to make progress. 

lassitude

noun
  • Listlessness or languor. 

  • Lethargy or lack of energy; fatigue. 

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