juice, broth
瀋 centers on liquid extracted from food: juice or broth. It refers to the flavorful liquid that comes from cooking or pressing ingredients.
瀋 combines the water radical 氵 with 審, which likely contributes the sound and may relate to examining or judging, perhaps suggesting the careful extraction of liquid. The exact historical development is uncertain.
Water 氵 is poured over something being examined 審, like inspecting ingredients to extract their juice or broth.
For シン, imagine a thin, clear broth being poured into a bowl: thin -> シン, and the liquid is the flavorful juice.
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Shenyang (China)