empireyoudaoicibaDictYouDict[empire 词源字典]
empire: [13] Empire and its close relatives emperor [13], imperial [14], imperious [16], and imperative [16] all come ultimately from the Latin verb imperāre ‘command’. This was a compound verb formed from the prefix in- ‘in relation to’ and parāre ‘make ready’ (source of English prepare), and hence originally meant ‘make preparations for’ before shifting metaphorically to ‘issue commands for’.

Of its derivatives, imperātor (source of English emperor) was used originally for ‘commander of an army’, and only secondarily for the ruler of the Roman empire, while the primary sense of imperium (source of English empire) was ‘a command’, and hence ‘authority’.
=> imperative, imperial, prepare[empire etymology, empire origin, 英语词源]
empire (n.)youdaoicibaDictYouDict
early 14c., from Old French empire "rule, authority, kingdom, imperial rule" (11c.), from Latin imperium "a rule, a command; authority, control, power; supreme power, sole dominion; military authority; a dominion, realm," from imperare "to command," from assimilated form of in- "in" (see in- (2)) + parare "to order, prepare" (see pare).
[P]roperly an empire is an aggregate of conquered, colonized, or confederated states, each with its own government subordinate or tributary to that of the empire as a whole. [Century Dictionary]
Not etymologically restricted to "territory ruled by an emperor," but used that way. The Empire, meaning "the British Empire," first recorded 1772 (it officially devolved into "The Commonwealth" in 1931); before that it meant the Holy Roman Empire (1670s). Empire as the name of a style (especially in reference to a style of dresses with high waistlines) is by 1869, in reference to the affected classicism prevailing in France during the reign of Napoleon I (1804-15). Second Empire is in reference to the rule of Napoleon III of France (1852-70). New York has been called the Empire State since 1834.