piazza vs shopping center

piazza

noun
  • A roofed gallery or arcade (for example around a public square or in front of a building). 

  • A public square, especially in Italian cities. 

shopping center

noun
  • An area, either enclosed or unenclosed, hosting multiple retail establishments; a shopping mall. 

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