oral history vs oral tradition

oral history

noun
  • Oral tradition. 

  • The collection and study of historical information about individuals, families, important events, or everyday life using audiotapes, videotapes, or transcriptions of planned interviews. 

oral tradition

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

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