grouping vs pecking order

grouping

noun
  • The action of the verb to group. 

  • A collection of things or people united as a group. 

  • Shot grouping. 

pecking order

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

  • 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. 

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