bridgework vs gangboard

bridgework

noun
  • The component parts of a bridge. 

  • The construction or repair of bridges. 

  • A partial denture that is anchored to existing teeth. 

gangboard

noun
  • A board or plank used as a temporary footbridge between a ship and a dockside or any gap such as scaffolding. 

  • The boards ending the hammock-nettings at either side of the entrance from the accommodation-ladder to the deck. 

  • A board or plank placed within or without the bulwarks of a vessel's waist for lookouts to walk or stand on. 

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