Ormazda, god of the Zoroastrians (extended to god of the Manicheans)
祆 centers on a specific Zoroastrian deity: Ormazda (Ahura Mazda), the supreme god. The meaning was later extended to include the god of the Manicheans, but the core remains a named divine figure rather than a general concept.
祆 combines 示 (altar, religious) with 天 (heaven), likely created to represent a foreign supreme deity associated with heaven. The exact historical development is uncertain, but the components suggest a constructed character for a specific religious context.
An altar 示 to heaven 天: picture a Zoroastrian fire altar under the open sky, dedicated to the supreme god Ormazda.
For ケン, imagine Ken, a devoted Zoroastrian priest, standing at the altar 示 beneath the heavens 天, chanting to Ormazda: Ken -> ケン.
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Zoroastrianism (esp. in China)