sleet, slush, name of a wetland
淕 centers on a cold, wet mixture: sleet or slush. The wetland name sense is a specific application of that same watery, half-frozen idea.
淕 combines 氵 (water) with 坴, which likely contributes the sound. The exact historical development is uncertain, but the water radical fits the sleet/slush meaning.
Water 氵 beside 坴 (a mound of earth) suggests a cold, wet mix: imagine sleet and slush piling up like a muddy mound.
For リク, picture a slick patch of sleet that makes you slip: slick -> リク, and the icy water 氵 beside the mound 坴 is dangerously slick.
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