pirog vs tortilla

pirog

noun
  • A baked case of dough with a sweet or savoury filling, popular in Eastern Europe. 

tortilla

noun
  • A flat round bread made out of cornmeal or flour. 

  • Spanish omelette; an omelette containing potatoes and onions. 

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