lower arm vs middle finger

lower arm

noun
  • The section of an arm from the elbow to the wrist; forearm. 

middle finger

noun
  • The finger between the forefinger and the ring finger 

  • An obscene gesture directed towards another as an insult, made by sticking up the middle finger of a hand. 

  • An insult directed at someone. 

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