cultivar vs refinement

cultivar

noun
  • A cultivated (not necessarily botanical) variety of a plant species or hybrid of two species. 

refinement

noun
  • High-class style; cultivation. 

  • The act, or the result of refining; the removal of impurities, or a purified material 

  • A fine or subtle distinction. 

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