mutedness vs slackness

mutedness

noun
  • The state or quality of being muted. 

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 mutedness and slackness occurred in a corpus of books? (source: Google Ngram Viewer )