companion vs retrofit

companion

noun
  • An appended source of media or information, designed to be used in conjunction with and to enhance the main material. 

  • A knot in whose neighborhood another, specified knot meets every meridian disk. 

  • A friend, acquaintance, or partner; someone with whom one spends time or accompanies 

  • A celestial object that is associated with another. 

  • A knight of the lowest rank in certain orders. 

  • The covering of a hatchway on an upper deck which leads to the companionway; the stairs themselves. 

  • The framework on the quarterdeck of a sailing ship through which daylight entered the cabins below. 

  • A thing or phenomenon that is closely associated with another thing, phenomenon, or person. 

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 companion and retrofit occurred in a corpus of books? (source: Google Ngram Viewer )