earphones vs stethoscope

earphones

noun
  • A pair of small loudspeakers worn inside each outer ear or covering all or part of the ear, without a connecting band worn over head. 

stethoscope

noun
  • A medical instrument used for listening to sounds produced within the body. 

verb
  • To auscultate, or examine, with a stethoscope. 

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