Burlington bun vs bismarck

Burlington bun

noun
  • A jelly doughnut. 

bismarck

noun
  • A doughnut filled with cream, often with chocolate icing. 

  • A fried cruller, or a sort of pancake. 

  • A jelly doughnut: a doughnut filled with jam and coated with sugar. 

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