portico vs terracing

portico

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

terracing

noun
  • A terraced structure. 

  • A series of terraces. 

  • A stand with a series of tiers. 

  • The formation of terraces. 

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