The word "emperor" started as a Roman military rank — imperator just meant "commander" — before becoming the supreme title of Western civilization.
The sovereign ruler of an empire, ranking above a king. Historically, a title originating from Roman military commanders.
From Old French empereor, from Latin imperator meaning 'commander, ruler,' from imperare ('to command'), from in- ('into, upon') + parare ('to prepare, order'). Originally a military title of honor in the Roman Republic. Key roots: *perh₂- (Proto-Indo-European: "to produce, bring forth, prepare"), imperare (Latin: "to command"), imperator (Latin: "commander-in-chief").
The German word Kaiser and the Russian word tsar/czar are NOT cognates of "emperor" — they both derive from Caesar, Julius Caesar's family name, which became a title. So two of Europe's most important words for "emperor" come from a man's surname rather than from Latin imperator. Meanwhile, Japan's emperor is called tennō (天皇, "heavenly sovereign"), a title that dates