libretto vs writing

libretto

noun
  • A book containing such a text. 

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

writing

noun
  • A work of an author. 

  • Something written, such as a document, article or book. 

  • The process of representing a language with symbols or letters. 

  • The style of writing of a person. 

  • Intended for or used in writing. 

  • Graphism of symbols such as letters that express some meaning. 

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