common raven vs onyx

common raven

noun
  • A dark-colored South Asian swallowtail butterfly, Papilio castor 

  • A large all-black passerine bird in the crow family, Corvus corax. 

onyx

noun
  • Any of various lycaenid butterflies of the genus Horaga. 

  • A jet-black color, named after the gemstone. 

  • A banded variety of chalcedony, a cryptocrystalline form of quartz. 

adj
  • jet-black 

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