chestnut tree vs pistachio

chestnut tree

noun
  • A tree that bears chestnuts; a tree of the genus Castanea 

pistachio

noun
  • The nutlike fruit of this tree. 

  • A pale green colour, like that of a pistachio seed. 

  • A deciduous tree (Pistacia vera) grown in parts of Asia for its drupaceous fruit. 

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