cochlea vs headphone

cochlea

noun
  • The complex, spirally coiled, tapered cavity of the inner ear of higher vertebrates, which contains the organ of Corti and in which sound vibrations are converted into nerve impulses. 

  • A spiral-shaped shell, especially that of a snail. 

headphone

noun
  • A cushioned speaker placed on, over, or inside the ear, normally used in left/right pairs. 

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