cubit vs ulna

cubit

noun
  • The distance from the elbow to the tip of the middle finger used as an informal unit of length. 

  • Any of various units of length approximating this distance, usually around 35–60 cm. 

ulna

noun
  • The bone of the forearm that extends from the elbow to the wrist on the side opposite to the thumb, corresponding to the fibula of the hind limb. Also, the corresponding bone in the forelimb of any vertebrate. 

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