folium vs turnsole

folium

noun
  • Synonym of turnsole (“purple dye”) 

  • A curve of the third order, consisting of two infinite branches having a common asymptote. The curve has a double point, and a leaf-shaped loop. 

  • A leaf, especially a thin leaf or plate. 

turnsole

noun
  • A purple dye obtained from Chrozophora tinctoria. 

  • A heliotrope; so named because its flowers are supposed to turn toward the sun. 

  • The euphorbiaceous plant Chrozophora tinctoria. 

  • A sunflower. 

  • A sun spurge (Euphorbia helioscopia). 

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