dripstone vs porch

dripstone

noun
  • A protective moulding over a door or window that allows rain to drip away from the structure. 

  • Stalactites and stalagmites collectively. 

  • A water filter in which impurities are removed by running water through a porous stone. 

porch

noun
  • A covered entrance to a building, whether taken from the interior, and forming a sort of vestibule within the main wall, or projecting without and with a separate roof. A porch often has chair(s), table(s) and swings. 

  • A portico; a covered walk. 

  • The platform outside the external hatch of a spacecraft. 

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