doner kebab vs kushiyaki

doner kebab

noun
  • A Turkish dish in which meat (typically seasoned lamb or mutton, but alternatively chicken or perhaps beef) is grilled on a revolving vertical spit; when cooked, the meat is sliced off and served with fresh vegetables in pita or rolled in a piece of unleavened flatbread. 

kushiyaki

noun
  • A Japanese technique for serving chicken or other foods on a skewer. 

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