pierogi vs xianbing

pierogi

noun
  • A square- or crescent-shaped dumpling of unleavened dough, stuffed with sauerkraut, cheese, mashed potatoes, cabbage, onion, meat, or any combination of these, or with a fruit filling. 

xianbing

noun
  • A traditional kind of Chinese stuffed pancake. 

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