lead-in vs preface

lead-in

noun
  • An introduction; something that leads into the beginning of something. 

  • A short phrase that begins the caption of a photograph. 

  • A region of data at the beginning of a compact disc, holding the table of contents. 

preface

noun
  • The beginning or introductory portion that comes before the main text of a document or book. 

  • An introduction, or series of preliminary remarks. 

  • A title or epithet. 

  • The prelude or introduction to the canon of the Mass. 

verb
  • To give a preface to. 

  • To introduce or make a comment before (the main point). 

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