bird dog vs espy

bird dog

verb
  • To watch closely. 

  • A multiservice tactical brevity code requesting configuration of sensors. 

  • To seek out. 

noun
  • A dog, especially a pointer, used in shooting to retrieve the dead birds. 

  • A tout. 

  • A person who seeks out real estate investment opportunities in exchange for a fee. 

  • A person who tries to steal someone else's romantic partner 

  • A radar detector (for detecting police speed traps). 

  • A hyperextension exercise performed lying on the knees, with one arm and the opposite leg lifted. 

espy

verb
  • To see (someone or something) without foreplanning or unexpectedly. 

  • To find out or observe (someone or something, especially if not easy to see) by spying or looking; to catch sight of; to see; to spot. 

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