fuck finger vs ring finger

fuck finger

noun
  • The middle finger 

ring finger

noun
  • Finger between middle finger and little finger; the "third finger" (UK) or the "fourth finger" (US), especially of the left hand. (The ring finger is the left hand; a ring finger is either hand.) 

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