fire hydrant vs hydrant

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. 

hydrant

noun
  • An outlet from a liquid/fluid main often consisting of an upright pipe with a valve attached from which fluid (e.g. water or fuel) can be tapped. 

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