slackness vs sluggishness

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. 

sluggishness

noun
  • The property of being sluggish, unable or unwilling to act quickly. 

  • The state of economic decline, inactivity, slow or subnormal growth. 

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