invasion vs shelter

invasion

noun
  • A military action consisting of armed forces of one geopolitical entity entering territory controlled by another such entity, generally with the objective of conquering territory or altering the established government. 

  • The breaching of the skin barrier. 

  • The spread of cancer cells, bacteries and such to the organism. 

  • The entry without consent of an individual or group into an area where they are not wanted. 

shelter

verb
  • To take cover. 

  • To provide cover from damage or harassment; to shield; to protect. 

noun
  • A refuge, haven or other cover or protection from something. 

  • An institution that provides temporary housing for homeless people, battered women, etc. 

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