passport vs travel book

passport

noun
  • An official document normally used for international journeys, which proves the identity and nationality of the person for whom it was issued. 

  • Any document that allows entry or passage. 

  • Something which enables someone to do or achieve something. 

verb
  • To enable eligibility for a benefit automatically based on eligibility for a different benefit. 

  • Providing the legal requirements to enable or legitimize cross-border economic activity. 

  • To regulate how money given to a local authority must be spent. 

travel book

noun
  • A book about travelling to a certain region, such as a memoir or guide book. 

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