Every free action has a moral cause, the will, and a physical cause, the power to act. ...The body politic has the same moving causes, namely the legislative power, and executive power. Nothing should be done without their concurrence.
Gist of Idea
The state has a legislature and an executive, just like the will and physical power in a person
Jean-Jacques Rousseau (The Social Contract (tr Cress) , III.01)
[compressed] This terminology is now standard in political philosophy. An absolute monarch like Edward III presumably embodies both branches.
Rousseau,Jean-Jacques: 'The Basic Political Writings', ed/tr. Cress,Donald A. [Hackett 1987], p.173