enhance vs retrofit

enhance

verb
  • To improve something by adding features. 

  • To augment or make something greater. 

  • To take up contrast agent (for an organ, tissue, or lesion). 

  • To be raised up; to grow larger. 

retrofit

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