realmyoudaoicibaDictYouDict[realm 词源字典]
realm: [13] Realm., régime, and regimen are ultimately the same word. All three come from Latin regimen ‘system of government’, a derivative of the verb regere ‘rule’ (from which English gets rector, regent, register, etc). This passed into Old French, where reiel ‘royal’ was grafted into it, producing realme – whence English realm.
=> rector, regal, régime, regimen, register, royal[realm etymology, realm origin, 英语词源]
realm (n.)youdaoicibaDictYouDict
late 13c., "kingdom," from Old French reaume, probably from roiaume "kingdom," altered (by influence of Latin regalis "regal") from Gallo-Roman *regiminem, accusative form of Latin regimen "system of government, rule" (see regimen). Transferred sense "sphere of activity" is from late 14c.