bibcock vs fire hydrant

bibcock

noun
  • An appliance (typically a valve with a threaded outlet) allowing the provision of hose connections outside of buildings. 

fire hydrant

noun
  • A device used by firefighters to obtain water from the main supply, consisting of a barrel, connections for hose and a valve assembly. 

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