paperback vs speller

paperback

noun
  • A book with flexible binding. 

adj
  • Having flexible binding. 

verb
  • To issue or publish (a book) in a paperback edition. 

speller

noun
  • A book used to learn how to spell properly. 

  • A person who spells. 

  • A spell checker. 

  • A participant in a spelling bee. 

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