apprehensiveness vs serenity

apprehensiveness

noun
  • the state of being apprehensive 

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. 

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