downland vs tor

downland

noun
  • An area of rolling hills (downs), often grassy pasture over chalk or limestone. 

tor

noun
  • A craggy outcrop of rock on the summit of a hill, created by the erosion and weathering of rock. 

  • A hill with such rock formation. 

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