bollard vs fence post

bollard

noun
  • A strong vertical post of timber or iron, fixed to the ground and/or on the deck of a ship, to which the ship's mooring lines etc are secured. 

  • A similar post preventing vehicle access to a pedestrian area, to delineate traffic lanes, or used for security purposes. 

fence post

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