annex vs envelopment

annex

noun
  • An addition, an extension. 

  • An appendix to a book or document. 

  • An addition to the territory of a country or state, from a neighbouring country or state, normally by military force. 

  • An addition or extension to a building. 

verb
  • To attach or connect, as a consequence, condition, etc. 

  • To join; to be united. 

  • To add something to another thing, especially territory; to incorporate. 

envelopment

noun
  • The act of enveloping. 

  • An offensive action in which an attacking force moves over or around the enemy and attacks from the rear; see also pincer movement. 

  • That which envelops; a covering. 

  • An action to seize the opponent's blade in one line and lead it (without losing contact) through a full circle to end in the same line. 

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