citizenship vs naturalization

citizenship

noun
  • The status of being a citizen, in its various senses. 

  • The state of being a citizen, in its various senses. 

naturalization

noun
  • The action of naturalizing somebody; act of granting citizenship. 

  • The introduction and establishment of an animal or plant into a place where it is not indigenous. 

  • The admission or adoption of foreign words or customs into general use. 

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