light bulb vs top light

light bulb

noun
  • An article that resembles such a bulb and converts electricity to light by any process. 

  • An evacuated glass bulb containing a metal filament which is heated by electrical resistance to produce light. 

  • Used in reference to the sudden arrival of a realization, an inspiration, an idea, or the like. 

top light

noun
  • Light from above; toplighting. 

  • Any glazing above a main window, partition or door 

  • A skylight. 

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

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