cognac vs whiskey

cognac

noun
  • A brandy distilled from white wine in the region around Cognac in France. 

whiskey

noun
  • A drink of whiskey. 

  • A light gig or carriage; a tim-whiskey. 

  • A liquor distilled from the fermented mash of grain (as rye, corn, or barley). 

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