buckeye vs horse chestnut

buckeye

noun
  • Any of several species of trees of the genus Aesculus. 

  • Any of several species of the related Mexican buckeye (genus Ungnadia). 

  • The seed or fruit of these plants. 

  • A native or resident of the American state of Ohio. 

  • The Junonia coenia butterfly. 

  • A confection made from peanut butter fudge partially dipped in chocolate to leave a circle of peanut butter visible, supposed to resemble the nut of the Ohio buckeye tree. 

  • Aesculus hippocastanum, the horse chestnut. 

horse chestnut

noun
  • Any of several tree species of genus Aesculus, especially Aesculus hippocastanum, common in temperate northern hemisphere. 

  • The large nutlike seed of these trees. 

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