big cat vs king of beasts

big cat

noun
  • Any large feline animal, especially one of the Panthera genus, including tigers, lions, jaguars and leopards. 

  • Used other than figuratively or idiomatically: see big, cat. 

king of beasts

noun
  • The lion. 

How often have the words big cat and king of beasts occurred in a corpus of books? (source: Google Ngram Viewer )