copper vs redbird

copper

noun
  • Any of various lycaenid butterflies with copper-coloured upperwings, especially those of the genera Lycaena and Paralucia. 

  • The reddish-brown colour/color of copper. 

  • A police officer. 

  • A reddish-brown, malleable, ductile metallic element with high electrical and thermal conductivity, symbol Cu, and atomic number 29. 

verb
  • To sheathe or coat with copper. 

adj
  • Made of copper. 

  • Having the reddish-brown colour/color of copper. 

redbird

noun
  • Any of several unrelated American songbirds having red plumage, especially the tanager or cardinal. 

  • Any of various red cars formerly used in the New York City subway system; or a train of such cars. 

  • A capsule of secobarbital. 

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