annex vs headquarters

annex

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. 

noun
  • 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, an extension. 

  • An addition or extension to a building. 

headquarters

noun
  • The center of an organization's operations or administration. 

  • The military installation from which troops are commanded and orders are issued; the military unit consisting of a commander and his support staff. 

  • A place of concentrated activity or influence. 

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