This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
宨 combines 宀 (roof) with 兆 (omen, sign). The exact historical development is uncertain, and the character is rare in modern use.
With no clear meaning, picture a roof 宀 over a mysterious omen 兆: something hidden and uncertain.
For チョウ, imagine a long-serving chief named Chou peering under the roof at a strange omen: Chou -> チョウ.