necessity vs retrofit

necessity

noun
  • Something which makes an act or an event unavoidable; an irresistible force; overruling power. 

  • Greater utilitarian good; used in justification of a criminal act. 

  • Indispensable requirements (of life). 

  • The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism. 

  • The condition of being needy; desperate need; lack. 

  • Something necessary; a requisite; something indispensable. 

  • The quality or state of being necessary, unavoidable, or absolutely requisite. 

retrofit

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. 

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. 

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