earmuff vs earphones

earmuff

noun
  • A sound-deadening cup or a pair of such cups worn over the ear or ears. 

  • A garment to keep the ears warm. 

  • A garment or part worn over a single ear. 

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. 

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