amethyst vs lilac

amethyst

noun
  • A purple colour. 

  • The tincture purpure, when emblazoning the arms of the English nobility. 

  • A transparent purple variety of quartz, used as a gemstone. 

adj
  • Having a colour similar to that of the gemstone 

lilac

noun
  • A pale purple color, the color of some lilac flowers. 

  • A flower of the lilac shrub. 

  • A large shrub of the genus Syringa, especially Syringa vulgaris, bearing white, pale-pink, or purple flowers. 

adj
  • Having a pale purple colour. 

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