pass through vs porthole

pass through

noun
  • A framed, window-like aperture in the interior wall of a house, usually between a kitchen and dining room, through which items (especially food) can be passed. A serving hatch. 

verb
  • To undergo; to experience. 

  • To infiltrate. 

  • To transit something. 

  • To make something move through something else. 

porthole

noun
  • A circular window set in the hull of a ship. 

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