citole vs gittern

citole

noun
  • An archaic musical instrument whose exact form is uncertain, generally shown with four strings 

gittern

noun
  • A small, quill-plucked, gut-strung musical instrument, most commonly with three to four strings in doubles courses; it is a flat-backed predecessor of the guitar, and it originated around the 13th century, coming to Europe via Moorish Spain. 

verb
  • To play on the gittern. 

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