mass murder vs slay

mass murder

noun
  • The killing of a large number of people over a short period of time. 

slay

verb
  • To defeat; to overcome (in a competition or contest). 

  • To kill; to murder. 

  • To amaze, stun, or otherwise incapacitate by excellence; to excel at something. 

  • To have sex with. 

  • To delight or overwhelm, especially with laughter. 

  • To eradicate or stamp out. 

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