libretto vs words

libretto

noun
  • A book containing such a text. 

  • The text of a dramatic musical work, such as an opera. 

words

noun
  • Lyrics. 

  • Angry debate or conversation; argument. 

  • Lines in a script for a performance. 

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