tarpan vs wild horse

tarpan

noun
  • An extinct Northern European wild horse, Equus ferus ferus. 

wild horse

noun
  • A member of the species Equus ferus, sometimes excluding the domesticated horse. 

  • A feral horse. 

  • An untamed horse. 

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