dirty, useless, weak, powerless, cracked, flaw
窳 centers on a state of being flawed, weak, or useless—something that is dirty, cracked, or powerless. The meanings all point to a lack of soundness or effectiveness.
窳 is a rare character. The top component 穴 (hole, cave) and the bottom component 㼌 (a variant of 窳 itself, or related to 瓜 with a phonetic role) suggest a meaning related to a hollow or flawed container, but the exact historical development is uncertain.
A hole (穴) in a container (㼌, resembling a gourd or vessel) makes it cracked and useless—dirty water leaks out, leaving it weak and powerless.
For ワ, imagine a cracked pot that makes a 'wa' sound as water leaks out—like a weak, powerless sigh: wa -> ワ.