river in Shaanxi, murky torrent
涔 centers on a specific river in Shaanxi and the idea of murky, turbid water. The torrent sense extends naturally from the image of a muddy, rushing stream.
涔 combines the water radical 氵 with 岑, which likely provides the sound and may relate to a steep or high place, suggesting a mountain torrent or a specific river name.
Water 氵 beside 岑, a shape that suggests a steep mountain. Picture a murky torrent rushing down a mountain slope in Shaanxi.
For サン, imagine the sun (サン) beating down on the murky river, making the water look even muddier: sun -> サン.
falling heavily (of rain, snow, etc.)