flathead (fish), (kokuji)
鯒 is a kokuji (Japan-made kanji) for a specific fish: the flathead. Its meaning is narrow and concrete, referring to that particular species.
鯒 is a kokuji created in Japan by combining 魚 (fish) with 甬, which likely contributes the sound こち. The exact historical reasoning behind the choice of 甬 is uncertain.
The left side 魚 means fish, and the right side 甬 looks a bit like a flat, wide head with a body. Picture a flathead fish swimming sideways: its broad head matches the shape of 甬.
For こち, imagine a flathead fish named Kotchi (like a nickname). When you call it, it comes swimming: Kotchi -> こち.
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