daybreak, bright and brilliant
暠 centers on the bright light of early morning: the moment of daybreak when the sun rises and everything becomes brilliant and clear.
暠 combines 日 (sun) with 高 (tall, high), suggesting the sun rising high and bringing bright daylight. The exact historical development is uncertain, but the component relationship is straightforward.
The sun 日 sits high 高 in the sky at daybreak, making everything bright and brilliant.
For コウ, imagine the sun rising high and a rooster crowing "ko-ke-kok-kou!" at daybreak: the crowing sound cues コウ while the sun climbs high.
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