people's republic vs popular republic

people's republic

noun
  • A particular area with strong left-leaning tendencies, especially one with a certain level of autonomy. 

  • Used other than figuratively or idiomatically: see people, 's, republic. 

  • A self-designation of states with Marxist-Leninist governments. 

popular republic

How often have the words people's republic and popular republic occurred in a corpus of books? (source: Google Ngram Viewer )