muddiness
濘 centers on the state of being muddy or miry, describing ground or water thick with soft, wet dirt.
濘 combines 氵 (water) with 寧, which likely contributes the sound and suggests a settled, stagnant quality, giving the idea of muddy water.
Water 氵 beside 寧 (a shape associated with calm or settled) suggests still, murky water that has become muddy.
For ネイ, imagine a horse neighing as it struggles through deep mud: neigh -> ネイ, and the muddiness makes every step difficult.