bibcock vs petcock

bibcock

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

petcock

noun
  • A small valve, spout, or faucet operated by hand, usually used to release pressure or drain fluid. 

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