This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
瑒 combines 王 (jade) with 昜, which likely contributes the sound. The exact historical development is uncertain.
The left side 王 suggests jade or a precious stone, while the right side 昜 is a common phonetic component. Without a clear meaning, picture a rare, unnamed gemstone with a bright, sun-like (昜) luster.
For チョウ, imagine a long-serving chief named Chou polishing a mysterious jade stone: Chou -> チョウ, and the stone's name is unknown.