ill-usage vs mistreatment

ill-usage

noun
  • bad, cruel or unkind treatment 

mistreatment

noun
  • Cruel, abusive , bad, unfair, or thoughtless treatment of a person or animal (only rarely of an object or a machine; usually: mishandle). 

How often have the words ill-usage and mistreatment occurred in a corpus of books? (source: Google Ngram Viewer )