esplanade vs quadrangle

esplanade

noun
  • A clear space between a citadel and the nearest houses of the town. 

  • The glacis of the counterscarp, or the slope of the parapet of the covered way toward the country. 

  • A grass plat; a lawn. 

  • Any clear, level space used for public walks or drives; especially, a terrace by the seaside. 

quadrangle

noun
  • The buildings forming the border of such a courtyard. 

  • A geometric shape with four angles and four straight sides; a four-sided polygon. 

  • A courtyard which is quadrangular. 

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