folklore vs oral tradition

folklore

noun
  • The tales, legends, superstitions, and traditions of a particular ethnic population. 

  • The tales, superstitions etc. of any particular group or community. 

  • The collective of proofs or techniques which are widely known among mathematicians, but have never been formally published. 

oral tradition

noun
  • Cultural material transmitted orally from one generation to another. 

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