hydrant vs injector

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. 

injector

noun
  • An apparatus by which a stream of water is forced into a steam boiler. 

  • An object that realizes a dependency injection. 

  • One who injects (himself or herself with) psychoactive drugs. 

  • Any of various devices that are used to inject something. 

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