gradation vs pecking order

gradation

noun
  • The act of gradating or arranging in grades. 

  • A calibration marking. 

  • A passing by small degrees from one tone or shade, as of color, to another. 

  • A diatonic succession of chords. 

  • Apophony. 

  • A gradual change within one parameter, or an overlapping of two blocks of sound. 

  • A sequence of gradual, successive stages; a systematic progression. 

  • Any degree or relative position in an order or series. 

verb
  • To form with gradations. 

pecking order

noun
  • The usually informal hierarchy of authority or command, often partial or approximate, as determined by the especially natural propensity for domination of different members of a specific group over each other, such as older brothers and sisters over their younger siblings. 

  • The natural hierarchy of social status and dominance occurring in a group of birds. 

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