groundnut vs pistachio

groundnut

noun
  • A climbing vine, Apios americana, of eastern North America, having fragrant brownish flowers and small edible tubers. 

  • The nutlike tuber of such a plant, especially peanuts. 

  • A plant which bears its nutlike seeds underground, such as a peanut (Arachis hypogaea) or a Bambara groundnut (Vigna subterranea). 

  • Any similar plant having underground tubers. 

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 groundnut and pistachio occurred in a corpus of books? (source: Google Ngram Viewer )