Quote by Northrop Frye
The metaphor of the king as the shepherd of his people goes back to ancient Egypt. Perhaps the use of this particular convention is due to the fact that, being stupid, affectionate, gregarious, and easily stampeded, the societies formed by sheep are most like human ones.
Summary
This quote suggests that the metaphor of a king being compared to a shepherd originates from ancient Egyptian culture. The reason behind this comparison could be that both sheep and humans share certain characteristics such as being foolish, affectionate, social, and prone to being easily influenced. The similarity between sheep societies and human societies could have led to this metaphorical convention.