What's the meaning of the phrase 'Pecking order'?
'Pecking order' is the name given to a form of hierarchy in which the most dominant takes precedence.
What's the origin of the phrase 'Pecking order'?
The form of social organisation called a pecking order was first observed in domestic hens.
It might be thought that the phrase refers to the order in which the animals eat - the dominant first and so on down to the weakest. It is the case that the dominant hens eat first, although this isn't quite how the term originated.
The pecking isn't of food but of each other. Hens are social animals and form themselves into a hierarchy. The dominance is established and maintained by pecking. The more dominant peck the less dominant and so on down the chain. A pecking order was the name given to the resulting hierachy.
For the origin of the expression we need to travel to Continental Europe. Enter the Norwegian zoologist Thorleif Schjelderup-Ebbe. In 1921 Schjelderup-Ebbe submitted a PhD dissertation on the behaviour of chickens. He called the dominance hierarchy Hackliste. This was later translated into German as Hackordnung and later, in the citation given below, into English as pecking order. That first usage in English is from K. C. Creasy's translation of Alverdes' Social Life in Animal World, 1927:
Such ‘pecking orders’ give the society concerned a certain degree of organization.
The term very quickly began to be used to describe social dominance in other animals, especially humans. The first example, of a 'non-poultry' figurative use is from the US newspaper The Pittsburgh Sun-Telegraph, October 1929:
Had Mrs. Gann been the wife of the Vice-President instead of the sister, her position of number two in the pecking order would never have been questioned.