reignyoudaoicibaDictYouDict
reign: [13] Reign goes back via Old French reignier to Latin rēgnāre ‘be king, rule’, a derivative of rēgnum ‘kingship’ (source of English interregnum [16]). This was closely related to rēx ‘king’ (source of English regal, royal, etc), and also to regere ‘rule’ (source of English rector, regent, etc).
=> interregnum, regent
reign (n.)youdaoicibaDictYouDict
early 13c., "kingdom," from Old French reigne "kingdom, land, country" (Modern French règne), from Latin regnum "kingship, dominion, rule, realm," related to regere (see regal). Meaning "period of rule" first recorded mid-14c.
reign (v.)youdaoicibaDictYouDict
"to hold or exercise sovereign power," late 13c., from Old French regner "rule, reign" (12c.), from Latin regnare "have royal power, be king, rule, reign," from regnum (see reign (n.)). Related: Reigned; reigning; regnal.