jebel vs sierra

jebel

noun
  • A hill, a mountain (especially in the Middle East or North Africa). 

sierra

noun
  • A rugged range of mountains. 

  • A relatively low-quality grade of Spanish saffron. 

  • A scombroid fish. 

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