dawdling, thoughtless, careless
顢 centers on a state of mental absence: dawdling, acting thoughtlessly, or being careless. The meanings share a lack of attentive focus.
顢 combines 頁 (head) with 㒼, which likely contributes the sound and may relate to covering or obscuring, suggesting a clouded or absent mind.
The left side 㒼 looks like a covered or blocked opening, and the right side 頁 means head. Picture a head with thoughts blocked or covered, leading to dawdling and careless mistakes.
For バン, imagine a person so thoughtless they ban their own head from thinking clearly: ban -> バン, and the blocked head 顢 becomes careless.