centralization vs flocking

centralization

noun
  • The act or process of centralizing, or the state of being centralized; the act or process of combining or reducing several parts into a whole 

flocking

noun
  • The process of adding small particles to a surface for the sake of texture. 

  • A material textured in this way, such as the artificial snow of a Christmas tree. 

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