extremity vs periphery

extremity

noun
  • The most extreme or furthest point of something. 

  • A hand or foot. 

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

  • An extreme measure. 

periphery

noun
  • The outside boundary, parts or surface of something. 

  • A first-rank administrative division of Greece, subdivided into provinces. 

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