expatriation vs refoulement

expatriation

noun
  • forced expulsion of from one's native land to another 

  • voluntary migration from one's native land to another 

refoulement

noun
  • Rendition of a person to an area (chiefly their country of origin) where they will face mistreatment, for example, expulsion of refugees into a war zone; (countable) an instance of this. 

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