co-wife vs wife

co-wife

noun
  • In a polygamous marriage, another wife of a woman’s husband. 

wife

noun
  • A married woman, especially in relation to her spouse. 

  • The female of a pair of mated animals. 

  • Synonym of woman. 

verb
  • to marry (a woman) 

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