fanlight vs tie beam

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 

tie beam

noun
  • a horizontal beam that serves to prevent two other structural members from separating while forming the base of a triangular truss for a pitched roof. 

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