tie-in vs zipper

tie-in

noun
  • An association or connection between things. 

  • Something that is related or connected to another thing. 

  • An authorized product based on a media property, such as a film or video game, by way of cross-promotion. 

zipper

noun
  • A string of clothes pegs or clips attached to the body and then quickly pulled off. 

  • A pressure-sensitive plastic closure. 

  • A leucine zipper. 

  • A zip fastener. 

  • A technique for arbitrarily traversing an aggregate data structure and updating its contents. See zipper (data structure). 

  • A scar on a person's body. 

verb
  • to put a zipper on an article. 

  • to close a zipper. 

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