flutterboard vs pontoon

flutterboard

noun
  • A buoyancy board made of foam, used to support the body when in water. 

pontoon

noun
  • A flat-bottomed boat or other floating structure used as a buoyant support for a temporary bridge, dock or landing stage. 

  • A lighter or barge used for loading or unloading ships. 

  • A bridge with floating supports. 

  • A float of a seaplane. 

  • A card game in which the object is to obtain cards whose value adds up to, or nearly to, 21 but not exceed it. 

  • A box used to raise a sunken vessel. 

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