nervure vs veinlet

nervure

noun
  • A vein in the wing of an insect. 

  • One of the ribs in a groined vault; a projecting moulding. 

veinlet

noun
  • A small or secondary vein, especially on the wing of an insect or the leaf of a plant. 

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