elementary vs foundation stone

elementary

noun
  • A supernatural being which is associated with the elements. 

  • An elementary school 

adj
  • Relating to the basic, essential or fundamental part of something. 

  • Relating to an elementary school. 

  • Relating to a subatomic particle. 

foundation stone

noun
  • The basis of something. 

  • A stone laid during the construction of a (usually important) building, the laying of which is usually marked by a ceremony. 

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