inertia vs sloth

inertia

noun
  • Lack of activity; sluggishness; said especially of the uterus, when, in labour, its contractions have nearly or wholly ceased. 

  • In a person, unwillingness to take action. 

  • The property of a body that resists any change to its uniform motion; equivalent to its mass. 

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 inertia and sloth occurred in a corpus of books? (source: Google Ngram Viewer )