birdman vs flying buttress

birdman

noun
  • an aviator. 

  • A man who works with birds. 

  • A mythological creature that is part man and part bird. 

flying buttress

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

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