European bison vs aurochs

European bison

noun
  • The wisent, species Bison bonasus, Europe's heaviest land animal. 

aurochs

noun
  • The European bison (Bison bonasus, or Europæus). 

  • An extinct European mammal, Bos primigenius, the ancestor of domestic cattle. 

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