earpiece vs mouthpiece

earpiece

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

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

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

mouthpiece

noun
  • The part of a telephone that is held close to the mouth. 

  • The part of a wind instrument that is held in or against the mouth. 

  • A lawyer for the defense. 

  • A spokesman; one who speaks on behalf of someone else. 

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