burian vs tumulus

burian

noun
  • A tomb; sepulchre. 

  • A camp; hill-fort. 

  • A barrow; mound; tumulus 

tumulus

noun
  • A mound of earth, especially one placed over a prehistoric tomb; a barrow. 

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