aerugo vs viridian

aerugo

noun
  • metallic rust, particularly of brass or copper; verdigris 

viridian

noun
  • A bluish-green pigment made from chromium sesquioxide. 

  • A bluish-green color. 

adj
  • Of a bluish green colour. 

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