hardback vs three-decker

hardback

noun
  • A book with a solid binding. 

adj
  • Having a solid binding. 

three-decker

noun
  • An old-fashioned pulpit. 

  • Anything with three layers or levels. 

  • A sailing warship that had guns on each of three decks. 

How often have the words hardback and three-decker occurred in a corpus of books? (source: Google Ngram Viewer )