copper vs dollar

copper

verb
  • To sheathe or coat with copper. 

noun
  • 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. 

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

adj
  • Made of copper. 

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

dollar

noun
  • A quarter of a pound or one crown, historically minted as a coin of approximately the same size and composition as a then-contemporary dollar coin of the United States, and worth slightly more. 

  • Official designation for currency in some parts of the world, including Canada, the United States, Australia, New Zealand, Hong Kong, and elsewhere. Its symbol is $. 

  • Money generally. 

  • Imported from the United States, and paid for in U.S. dollars. (Note: distinguish "dollar wheat", North American farmers' slogan, meaning a market price of one dollar per bushel.) 

  • A unit of reactivity equal to the interval between delayed criticality and prompt criticality. 

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