kolach vs pirozhki

kolach

noun
  • Type of pastry that holds a portion of fruit or cheese, surrounded by a puffy cushion of supple dough. 

pirozhki

noun
  • A single such pastry. 

  • Small pastries filled with finely chopped meat, vegetables or fruit baked or fried, from eastern European cuisine, or a serving of these. 

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