egress vs petcock

egress

verb
  • To exit or leave; to go or come out. 

noun
  • The process of exiting or leaving. 

  • The end of the transit of a celestial body through the disk of an apparently larger one. 

  • An exit or way out. 

petcock

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

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