buckeye vs conker tree

buckeye

noun
  • Aesculus hippocastanum, the horse chestnut. 

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

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

  • 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. 

conker tree

noun
  • The horse chestnut tree, Aesculus. 

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