defamation vs hit piece

defamation

noun
  • The act of injuring another person's reputation by any slanderous communication, written or oral; the wrong of maliciously injuring the good name of another. 

hit piece

noun
  • A published article or post aiming to sway public opinion by presenting false or biased information in a way that appears objective and truthful. 

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