flying buttress vs folder

flying buttress

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

folder

noun
  • A machine or person that folds things. 

  • An organizer that papers are kept in, usually with an index tab, to be stored as a single unit in a filing cabinet. 

  • A folding knife, typically a pocketknife. 

  • A virtual container in a computer's file system, in which files and other folders may be stored. The files and subfolders in a folder are usually related. 

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