sandfish, (kokuji)
鰰 is a Japanese kokuji (country-made character) that specifically names the sandfish, a local fish. It has no broader abstract meaning beyond this single referent.
鰰 is a Japanese kokuji created by combining 魚 (fish) with 神 (god, spirit). It was likely coined to name the sandfish, possibly reflecting a local cultural or religious association with the fish.
A fish (魚) so special it is associated with a god (神): the sandfish, a local delicacy or culturally significant catch.
For はたはた, imagine the sound of sandfish flopping on a deck: hata-hata, hata-hata. The repetitive flapping sound cues はたはた.
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