bract vs frond

bract

noun
  • A leaf or leaf-like structure from the axil out of which a stalk of a flower or an inflorescence arises. 

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 bract and frond occurred in a corpus of books? (source: Google Ngram Viewer )