place in Shandong province
郈 is a rare kanji that refers to a specific place name in Shandong province. Its standalone meaning is limited to this geographical reference.
郈 combines 后 with the village radical ⻏, suggesting a place name. The exact historical development is uncertain, but it likely originated as a geographical designation.
The left side 后 looks like a ruler, and the right side ⻏ is a village. Imagine a ruler's village in Shandong province: 郈 is that place.
For コウ, picture a coat of arms marking the ruler's village: coat -> コウ, and the coat hangs in the village hall.
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