inexertion vs slackness

inexertion

noun
  • Lack of exertion or effort; indolence; laziness. 

slackness

noun
  • The state of being slack; the quality of having slack. 

  • A subgenre of dancehall music with sexual lyrics. 

  • Vulgarity in West Indian culture. 

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