blackthorn vs heliotrope

blackthorn

noun
  • A stick or staff taken from this tree. 

  • A large shrub or small tree, Prunus spinosa, that is native to Europe, western Asia, and north Africa. It has a dark bark and bears thorns. 

heliotrope

noun
  • A plant that turns so that it faces the sun. 

  • A light purple or violet colour. 

  • Particularly, a purple-flowered plant of the species Heliotropium arborescens. 

  • A bloodstone (a variety of quartz). 

  • An instrument, employed in triangulation, that uses a mirror to reflect sunlight toward another, very distant, surveyor. 

  • The fragrance of heliotrope flowers. 

adj
  • Light purple or violet. 

  • Keeping one’s face turned toward the sun. 

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