late 14c., from Old French regal "royal" (12c.) or 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," hence, "direct in a straight line, rule, guide" (cognates: Sanskrit raj- "a king, a leader;" Avestan razeyeiti "directs;" Persian rahst "right, correct;" Latin regere "to rule," rex "a king, a leader," rectus "right, correct;" Old Irish ri, Gaelic righ "a king;" Gaulish -rix "a king," in personal names, such as Vircingetorix; Gothic reiks "a leader;" Old English rice "kingdom," -ric "king," rice "rich, powerful," riht "correct;" Gothic raihts, Old High German recht, Old Swedish reht, Old Norse rettr "correct"). Related: Regally.