bush telegraph vs jungle drums

bush telegraph

noun
  • A gossip network. 

  • A system used by undeveloped societies in remote regions for communication over long distances, such as drum sounds, word-of-mouth relay, or smoke signals. 

jungle drums

noun
  • An informal network of news and gossip; the grapevine. 

  • Drumming performed, or as performed, in the rituals of traditional pre-industrial societies. 

How often have the words bush telegraph and jungle drums occurred in a corpus of books? (source: Google Ngram Viewer )