bonus vs retrofit

bonus

noun
  • An extra sum given as a premium, e.g. to an employee or to a shareholder. 

  • Something extra that is good; an added benefit. 

  • An addition to the player's score based on performance, e.g. for time remaining. 

  • One or more free throws awarded to a team when the opposing team has accumulated enough fouls. 

verb
  • To pay a bonus, premium 

retrofit

noun
  • An act of supplying a device, structure, etc., with new components or parts that were not previously available or installed; a retrofitting. 

  • A change made to a device, structure, etc., by introducing components or parts that were not previously available or installed. 

verb
  • To supply (a device, structure, etc.) with new components or parts that were not previously available or installed; to modernize. 

  • Synonym of backport (“to retroactively supply a fix or feature to a previous version of a software product at the same time or after supplying it to the current version.”) 

  • To give new characteristics or make alterations (to someone or something) to suit them to changed circumstances. 

  • To supply a device, structure, etc., with new components or parts that were not previously available or installed. 

  • To add or substitute (new components or parts) that were not previously available for or installed in a device, structure, etc. 

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