weir, another name for Shanghai
滬 centers on a water barrier: a weir or dam-like structure. The Shanghai sense is a historical place name derived from a local fishing weir.
滬 combines 氵 (water) with 扈, which likely contributes the sound and relates to a barrier or enclosure. The character originally referred to a bamboo fishing weir used in the Shanghai area, later becoming a name for the region.
Water 氵 plus 扈 (which looks like a door 戸 over a mouth 口 and a coiled shape 巴) suggests a gate-like structure controlling water flow: a weir.
For コウ, imagine a koi fish swimming up to a weir: koi -> コウ, and the weir blocks its path.
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Shanghai (China)