slackness vs slushiness

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. 

slushiness

noun
  • The state or quality of being slushy. 

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