grievance vs rancor

grievance

noun
  • Feelings of being wronged; outrage. 

  • A formal complaint, especially in the context of a unionized workplace. 

  • A wrong or hardship suffered, which is the grounds of a complaint. 

  • Violation of regulations or objectionable behavior. 

  • A complaint or annoyance. 

  • Something which causes grief. 

rancor

noun
  • A feeling of long-lasting ire for another, sometimes to the point of hatred, over a perceived wrongdoing; bitterness. 

  • Rancidity, rankness. 

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