name of a Chinese river
淞 is a rare kanji used primarily as the name of a Chinese river. It has no clear standalone meaning beyond that proper-name use.
淞 combines the water radical 氵 with 松, which likely contributes the sound. The exact historical development is uncertain, but it is used as a river name.
The water radical 氵 beside 松 (pine) suggests a river named after or associated with pine trees. Picture a river flowing through a pine forest.
For ショウ, imagine the river's name being pronounced like 'show': show -> ショウ, as in a scenic show of pine trees along the riverbank.
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