litigate vs sue

litigate

verb
  • To go to law; to carry on a lawsuit. 

  • To dispute; to fight over. 

  • To contest in law. 

sue

verb
  • To file a legal action against someone, generally a non-criminal action. 

  • To clean (the beak, etc.). 

  • To leave high and dry on shore. 

  • To seek by request; to make application; to petition; to entreat; to plead. 

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