expulsion vs refoulement

expulsion

noun
  • The act of expelling or the state of being expelled. 

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 expulsion and refoulement occurred in a corpus of books? (source: Google Ngram Viewer )