cattle call vs introduction

cattle call

noun
  • An audition which is open to the public and thus draws a large number of applicants, many of whom are inexperienced. 

introduction

noun
  • A written or oral explanation of what constitutes the basis of an issue. 

  • The act or process of introducing. 

  • A means, such as a personal letter, of presenting one person to another. 

  • An initial section of a book or article, which introduces the subject material. 

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