king post vs piling

king post

noun
  • A central vertical supporting post used in architecture and bridge as well as in aircraft and ship design. 

piling

noun
  • A structural support comprising a length of wood, steel, or other construction material. 

  • The act of heaping up. 

  • The process of building up, heating, and working fagots or piles to form bars, etc. 

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