traitor, villain
宄 centers on a person who acts against order from within: a traitor or villain who causes internal disruption.
宄 combines 宀 (roof) with 九, which may have contributed a sound element. The character likely expressed the idea of internal wrongdoing or treachery under a roof.
Under a roof 宀, a figure like 九 sneaks around causing trouble—a traitor or villain working from within.
For キ, imagine a key villain hiding under the roof, holding a key to the house: key -> キ, and the traitor uses it to cause chaos.