agitated, alarmed
偟 centers on a state of inner disturbance: being agitated or alarmed. The given meanings describe a person unsettled and restless.
偟 combines the person radical 亻 with 皇, which likely contributes a phonetic element. The exact historical development is uncertain, but the character is associated with agitated or alarmed states.
A person 亻 beside an emperor 皇: imagine a nervous servant standing before the emperor, visibly agitated and alarmed by his presence.
For コウ, picture the agitated servant bowing low and uttering a nervous 'Kou...' (コウ) as he addresses the emperor 皇.