"a king," 1610s, from Latin rex (genitive regis) "a king," related to regere "to keep straight, guide, lead, rule" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule;" source also of Sanskrit raj- "king;" Old Irish ri "king," genitive rig).
person ruling as representative of a sovereign, 1520s, from French vice-roy, from Old French vice- "deputy" (see vice-) + roi "king," from Latin regem (nominative rex) "king," which is related to regere "to keep straight, guide, lead, rule" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). The species of American butterfly so called from 1881.
fem. proper name, from Latin, literally "queen;" related to rex (genitive regis) "king" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). Cognate with Sanskrit rajni "queen," Welsh rhyain "maiden, virgin." The capital city of Saskatchewan was named 1882 by the then-governor general of Canada, Marquess of Lorne, in honor of Queen Victoria.
"kingly, pertaining to a king," late 14c., from Old French regal "royal" (12c., Modern French réal) and directly from Latin regalis "royal, kingly; of or belonging to a king, worthy of a king," from rex (genitive regis) "king," from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule." Related: Regally.