forearm vs lower arm

forearm

noun
  • The part of the arm between the wrist and the elbow. 

  • A section of the weapon between the receiver and the muzzle, used to hold the firearm steady. 

verb
  • To arm in preparation. 

lower arm

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

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