viol vs viola d'amore

viol

noun
  • A stringed instrument related to the violin family, but held in the lap between the legs like a cello, usually with C-holes, a flat back, a fretted neck and six strings, played with an underhanded bow hold 

  • A large rope used to manipulate the anchor 

verb
  • To play the viol. 

viola d'amore

noun
  • A 7- or 6-stringed musical instrument similar to the treble viol, used chiefly in the Baroque period. 

How often have the words viol and viola d'amore occurred in a corpus of books? (source: Google Ngram Viewer )