joining vs tie-in

joining

noun
  • The act or result of joining; a joint or juncture. 

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. 

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