layer cake vs open sandwich

layer cake

noun
  • A cake consisting of multiple stacked sheets of cake, held together by frosting or jam, etc. 

  • A type of layering of materials, used in some nuclear bombs. 

open sandwich

noun
  • Any dish consisting of only one slice of bread, with any topping. 

How often have the words layer cake and open sandwich occurred in a corpus of books? (source: Google Ngram Viewer )