parapet vs tower block

parapet

noun
  • Part of a perimeter that extends above the roof. 

  • A fortification consisting of a wall. 

  • A low protective wall. 

  • Hyponym: balustrade 

tower block

noun
  • A tall residential or office building. 

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