chorten vs megalith

chorten

noun
  • A Tibetan stupa. 

megalith

noun
  • A prehistoric monument made up of one or more large stones. 

  • A large stone slab making up a prehistoric monument, or part of such a monument. 

  • A large stone or block of stone used in the construction of a modern structure. 

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