first-degree murder vs man-killer

first-degree murder

noun
  • An act that constitutes the crime of first-degree murder. 

  • The criminal offence of murder in a form considered by law to be the most serious; the precise distinction may vary by jurisdiction but typically involves premeditation, or the choice of victim or other circumstances being regarded as especially blameworthy. 

man-killer

noun
  • A murderer. 

  • An animal that kills humans. 

  • Someone who habitually seduces men. 

How often have the words first-degree murder and man-killer occurred in a corpus of books? (source: Google Ngram Viewer )