lode vs nervure

lode

noun
  • A vein of metallic ore that lies within definite boundaries, or within a fissure. 

  • A rich source of supply. 

  • A watercourse. 

nervure

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

  • A vein in the wing of an insect. 

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