daub
涴 centers on applying something wet or messy: daubing, smearing, or staining a surface with a liquid or paste.
涴 combines 氵 (water) with 宛, which likely contributes the sound and may relate to bending or curving, suggesting a liquid that is spread or smeared. The exact historical development is uncertain.
Water 氵 plus 宛 (which looks like a bent shape under a roof) suggests liquid being smeared or daubed onto a surface, like paint or mud.
For エン, imagine daubing a wall with paint while thinking of the English word 'end'—you daub until the end of the wall: end -> エン.
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