auburn vs cupreous

auburn

adj
  • Of a reddish-brown colour. 

noun
  • A dark reddish-brown colour, often used to describe hair colour. 

cupreous

adj
  • Of a reddish-brown color, like that of polished copper. 

  • Of or of the nature of copper. 

  • Containing copper. 

noun
  • A reddish-brown color, like that of polished copper. 

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