cheerfulness vs pessimism

cheerfulness

noun
  • The state of being cheerful; joy. 

pessimism

noun
  • A general belief that bad things will happen. 

  • The condition of being pessimal. 

  • The doctrine that this world is the worst of all possible worlds. 

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