extremity vs handspan

extremity

noun
  • A hand or foot. 

  • The most extreme or furthest point of something. 

  • A limb (“major appendage of a human or animal such as an arm, leg, or wing”). 

  • An extreme measure. 

handspan

noun
  • The distance between the outstretched tips of the little finger and thumb when used as a unit of measurement 

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