contentment vs serenity

contentment

noun
  • The state or degree of being contented or satisfied. 

  • happiness in one's situation; satisfaction 

  • The neurophysiological experience of satisfaction and being at ease in one's situation, body, and/or mind. 

serenity

noun
  • The state of being serene; calmness; peacefulness. 

  • A lack of agitation or disturbance. 

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

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