folium vs frond

folium

noun
  • A leaf, especially a thin leaf or plate. 

  • 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. 

  • Synonym of turnsole (“purple dye”) 

frond

noun
  • The leaf of a fern, especially a compound leaf. 

  • Any fern-like leaf or other object resembling a fern leaf. 

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