killing vs serial killer

killing

noun
  • An instance of someone being killed. 

  • A large amount of money. 

adj
  • That makes one ‘die’ with laughter; very funny. 

  • That literally deprives of life; lethal, deadly, fatal. 

serial killer

noun
  • A person who commits multiple (more than two) murders, especially similar ones with no obvious motive over a period of time with a "cooling-off" period between each murder. 

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