carnet vs detachable portion

carnet

noun
  • An admission pass. 

  • A ticket book, a collection of tickets in the form of a booklet often sold at a discount to single tickets. 

  • A customs document that allows the temporary duty-free importation of a particular article 

detachable portion

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