bush telegraph vs mulga wire

bush telegraph

noun
  • 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. 

  • A gossip network. 

mulga wire

noun
  • A system for long-distance communication used by Aboriginal Australians, chiefly using smoke signals; also, a message or signal sent using such a system. 

  • A message or story transmitted through such an informal network, especially one containing false information. 

  • An informal gossip network, especially in a rural area such as the outback; also, a component in the network (either a person or an imagined wire). 

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