portico vs revolving door

portico

noun
  • A porch, or a small space with a roof supported by columns, serving as the entrance to a building. 

revolving door

noun
  • A door that rotates around a central pivot. 

  • A movement of personnel between roles as legislators and regulators, on the one hand, and members of the industries affected by the legislation and regulation, on the other. 

  • A system or institution in which people exit and immediately reenter. 

  • Synonym of recidivism 

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