fanlight vs mullion

fanlight

noun
  • a semicircular or semioval window over a door or other window, normally having a fan-like structure of ribs; sometimes hinged to the transom 

  • an electric fan, usually a ceiling fan, that is also a light fixture 

mullion

noun
  • A vertical bar between the panes of glass or casements of a window or the panels of a screen. 

verb
  • To shape into divisions by means of mullions. 

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