battlement vs buttress

battlement

noun
  • The towering roof of heaven. 

  • In fortification: an indented parapet, formed by a series of rising members called cops or merlons, separated by openings called crenelles or embrasures, the soldier sheltering himself behind the merlon while he fires through the embrasure or through a loophole in the battlement. 

  • Any high wall for defense. 

buttress

noun
  • A feature jutting prominently out from a mountain or rock. 

  • A brick or stone structure built against another structure to support it. 

  • Anything that supports or strengthens. 

  • A buttress-root. 

  • Anything that serves to support something; a prop. 

verb
  • To support something or someone by supplying evidence. 

  • To support something physically with, or as if with, a prop or buttress. 

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