This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 侟 is uncertain. It visually combines 亻 (person) with 存, but the original semantic and phonetic roles are unclear.
A person 亻 beside 存, a shape associated with existence or preservation. Without a clear meaning, picture a person guarding something preserved, but treat the meaning as uncertain.
For セン, imagine a person 亻 standing beside a preserved 存 scroll worth one thousand 千 (せん) coins: 千 -> セン.
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