viceroy (n.)

person ruling as representative of a sovereign, 1520s, from Middle 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.