murus vs parapet

murus

noun
  • A wall. 

  • A pattern-forming ridge on the surface of a pollen grain. 

parapet

noun
  • A low protective wall. 

  • A fortification consisting of a wall. 

  • Part of a perimeter that extends above the roof. 

  • Hyponym: balustrade 

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