flour vs hardtack

flour

noun
  • Powder obtained by grinding or milling cereal grains, especially wheat, or other foodstuffs such as soybeans and potatoes, and used to bake bread, cakes, and pastry. 

  • Powder of other material. 

  • The food made by grinding and bolting cleaned wheat (not durum or red durum) until it meets specified levels of fineness, dryness, and freedom from bran and germ, also containing any of certain enzymes, ascorbic acid, and certain bleaching agents. 

  • Coordinate term: meal 

verb
  • To reduce to flour. 

  • To apply flour to something; to cover with flour. 

  • To break up into fine globules of mercury in the amalgamation process. 

hardtack

noun
  • A large, hard biscuit made from unleavened flour and water; formerly used as a long-term staple food aboard ships. 

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