lassitude vs sloth

lassitude

noun
  • Lethargy or lack of energy; fatigue. 

  • Listlessness or languor. 

sloth

noun
  • Laziness; slowness in the mindset; disinclination to action or labour. 

  • A herbivorous, arboreal South American mammal of the families Megalonychidae and Bradypodidae, noted for its slowness and inactivity. 

  • A collective term for a group of bears. 

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