This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
嶟 combines 山 (mountain) with 尊, which likely contributes a sound element. The exact historical development is uncertain.
A mountain 山 with a shape 尊 that suggests something towering or steep, but its meaning is not well established.
For ソン, imagine a son climbing a steep mountain: son -> ソン, and the mountain 山 is the setting.