serenity vs unkindness

serenity

noun
  • A lack of agitation or disturbance. 

  • The state of being serene; calmness; peacefulness. 

  • A title given to a reigning prince or similar dignitary. 

unkindness

noun
  • The state or quality of being unkind. 

  • An unkind act. 

  • The collective noun for ravens 

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