prototype vs under review

prototype

noun
  • An original form or object which is a basis for other forms or objects (particularly manufactured items), or for its generalizations and models. 

  • An early sample or model built to test a concept or process. 

  • A type of race car, a racing sports car not based on a production car. A 4-wheeled cockpit-seating car built especially for racing on sports car circuits, that does not use the silhouette related to a consumer road car. 

  • An instance of a category or a concept that combines its most representative attributes. 

  • A declaration of a function that specifies the name, return type, and parameters, but none of the body or actual code. 

verb
  • To create a prototype of. 

under review

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