earpiece vs listener

earpiece

noun
  • A speaker placed inside or held near to the ear. 

  • The arm on a pair of glasses that hooks over the ear to hold them in place. 

  • A receiver of a telephone to hold near to one's ear. 

listener

noun
  • A person's ear. 

  • Someone who listens, especially to a speech or a broadcast. 

  • A musical anthology. 

  • A function that runs in response to an event; an event handler. 

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