From Latin 'imperium' (command) — 'in-' + 'parare' (to order). Originally Roman executive authority, then the territory it ruled.
An extensive group of states or countries ruled over by a single monarch, an oligarchy, or a sovereign state; a large commercial organization controlled by one person or group.
From Old French 'empire,' from Latin 'imperium' (command, authority, dominion, realm), from 'imperāre' (to command), from 'in-' (in, upon) + 'parāre' (to prepare, arrange, order). The Latin 'imperium' originally denoted the absolute executive power granted to Roman consuls and praetors, the right to command armies and enforce law. It was extended metaphorically to the territory over which that power was exercised. The word 'emperor' comes
The title 'emperor' comes from Latin 'imperātor,' which originally just meant 'military commander' — Roman soldiers would shout it to hail a victorious general. Augustus adopted it as a permanent title, and it has meant 'supreme ruler' ever since, but its origin is purely military, not royal.