lede vs prolog

lede

noun
  • The introductory paragraph or paragraphs of a newspaper, or a news or other type of article; the lead or lead-in. 

prolog

noun
  • A speech or section used as an introduction, especially to a play or novel. 

  • A component of a computer program that prepares the computer to execute a routine. 

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