flageolet vs transverse flute

flageolet

noun
  • A type of small flute of the fipple family. 

  • A type of kidney bean, common in France. 

  • A technique for playing stringed instrument that produces high-pitched overtones. 

transverse flute

noun
  • Any type of flute that is held sideways when played. 

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