open sandwich vs wafer

open sandwich

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

wafer

noun
  • A light, thin, flat biscuit/cookie. 

  • A thin disk of consecrated unleavened bread used in communion. 

  • A soft disk originally made of flour, and later of gelatin or a similar substance, used to seal letters, attach papers etc. 

  • A thin disk of silicon or other semiconductor on which an electronic circuit is produced. 

verb
  • To seal or fasten with a wafer. 

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