armband vs armrest

armband

noun
  • A band worn around the arm, usually to symbolize protest or mourning. 

  • An inflatable band worn round the arms to keep afloat in water 

  • A band worn around the arm of the captain of a team. 

armrest

noun
  • Part of the seat of a chair that is designed to support the arm. 

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