heliotrope vs perpetual

heliotrope

adj
  • Light purple or violet. 

  • Keeping one’s face turned toward the sun. 

noun
  • 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. 

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

perpetual

adj
  • Flowering throughout the growing season. 

  • Set up to be in effect or have tenure for an unlimited duration. 

  • Continuing; uninterrupted. 

  • Lasting forever, or for an indefinitely long time. 

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