custard slice vs napoleon

custard slice

noun
  • Synonym of vanilla slice 

napoleon

noun
  • Other subsequent 20-franc coins, notes, or values. 

  • A person resembling Napoleon Bonaparte, (usually) in having come to dominate an area or sphere of activity through ruthlessness or illegality as well as surpassing ability. 

  • The franc germinal: a 20-franc gold coin issued under Napoleon. 

  • A 19th-century five-card trick-taking game simplified from euchre. 

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