hardship vs unhappiness

hardship

noun
  • Difficulty or trouble; hard times. 

  • A burden, a source of difficulty that could impose a barrier. 

verb
  • To treat (a person) badly; to subject to hardships. 

unhappiness

noun
  • The feeling of not being happy 

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