ラテン語のregalis, kingly, royalから、rex, kingから、PIE*reg, to straight, govern, rule, regulate, rightと同じ語源。
英語の語源
regal
regal: [14] Regal and royal are doublets: that is to say, they come from the same ultimate source, but have diverged over the centuries. This source was rēgālis, a derivative of Latin rēx ‘king’. This came from Indo-European *rēg-, which also produced the Sanskrit ancestor of English rajah, and was a lengthened version of *reg-, source of English rector, regiment, region, regular, reign, right, rule, etc. Regal was probably borrowed direct from Latin, whereas royal was routed via Old French. Also from rēx come regalia [16] and regicide [16]. => rajah, rector, regiment, region, regular, reign, right, royal, rule
regal (adj.)
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.
例文
1. His manner is not so much regal as professorial.