headphone vs headset

headphone

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

headset

noun
  • A pair of headphones or earphones, or a singular headphone or earphone, typically with an attached microphone. 

  • On a bicycle, the system of bearings that connects the fork to the frame. 

  • Any electronic device worn on the head. 

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