concubine vs sponsor

concubine

noun
  • A slave-girl or woman, kept for instance in a harem, who is held for sexual service. 

  • A sexual partner, especially a woman, to whom one is not or cannot be married. 

  • A woman who lives with a man, but who is not a wife. 

sponsor

verb
  • To be a sponsor for. 

noun
  • A person or organisation with some sort of responsibility for another person or organisation, especially where the responsibility has a religious, legal, or financial aspect. 

  • One that pays all or part of the cost of an event, a publication, or a media program, usually in exchange for advertising time. 

  • A senior member of a twelve step or similar program assigned to a guide a new initiate and form a partnership with him. 

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