flying buttress vs rung

flying buttress

noun
  • A buttress that stands apart from the structure that it supports, and is connected to it by an arch (flyer). 

rung

noun
  • A crosspiece between legs of a chair. 

  • A crosspiece forming a step of a ladder; a round. 

  • A position in a hierarchy. 

verb
  • simple past tense of ring 

adj
  • Of a pig: having a ring through the nose. 

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