externality vs superficies

externality

noun
  • A thing that is external relative to something else. 

  • The state of being external or externalized. 

  • An impact, positive or negative, on any party not involved in a given economic transaction or act. 

superficies

noun
  • The visible, external surface of a body. 

  • The area of a two-dimensional surface. 

  • The surface (of something immaterial, especially of the mind or soul). 

  • A building intimately associated with the land on which it is built. 

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