top light vs transom

top light

noun
  • The upper (and usually smaller) part (casement) of a window, often hinged a the top 

  • Any glazing above a main window, partition or door 

  • A skylight. 

  • Light from above; toplighting. 

transom

noun
  • A horizontal dividing bar in a window. 

  • The flat or nearly flat stern of a boat or ship. 

  • The horizontal beam on a cross or gallows. 

  • A crosspiece over a door; a lintel. 

  • Any of several transverse structural members in a ship, especially at the stern; a thwart. 

  • Items that have arrived over the transom. 

  • A transom window. 

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