This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
瓺 combines 镸 (long) and 瓦 (tile/earthenware). The exact historical development is uncertain, but it likely relates to a type of long earthenware vessel.
The left side 镸 suggests something long, and the right side 瓦 is earthenware. Picture a long clay pot or jar.
For チョウ, imagine a long earthenware jar named Chou: Chou -> チョウ, the long jar.