bird dog vs plod

bird dog

verb
  • To seek out. 

  • A multiservice tactical brevity code requesting configuration of sensors. 

  • To watch closely. 

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. 

plod

verb
  • To trudge over or through. 

  • To walk or move slowly and heavily or laboriously (+ on, through, over). 

  • To toil; to drudge; especially, to study laboriously and patiently. 

noun
  • A slow or labored walk or other motion or activity. 

  • the police, police officers 

  • a police officer, especially a low-ranking one. 

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