introduction vs voiding

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. 

voiding

noun
  • That which is voided; that which is ejected or evacuated; a remnant; a fragment. 

  • An act by which something is voided, such as urination. 

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