to inform quickly, an urgent communication
俈 centers on conveying information with speed and urgency: informing quickly or sending an urgent communication.
俈 combines 亻 (person) with 告 (inform, announce), suggesting a person delivering an urgent message. The exact historical development is uncertain, but the component relationship is straightforward.
A person 亻 beside 告 (inform) is someone who quickly passes on urgent news. Imagine a messenger rushing to deliver a critical announcement.
For コク, picture a person knocking urgently on a door to deliver a message: knock -> コク, and the person 亻 is informing 告 quickly.