hardship vs rigour

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. 

rigour

noun
  • Higher level of difficulty. 

  • A trembling or shivering response. 

  • Character of being unyielding or inflexible. 

  • Harshness, as of climate. 

  • Shrewd questioning. 

  • Severity or strictness. 

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