state in today's Henan province
鄶 refers to an ancient Chinese state located in what is now Henan province. Its meaning is a specific historical place name with no broader conceptual extensions.
鄶 combines 會 (meeting, gathering) with the city enclosure ⻏, likely representing the name of a feudal state. The exact historical origin of the place name is uncertain.
The left side 會 suggests a gathering, and the right side ⻏ is a city wall. Picture an ancient walled city where people gathered, the state of 鄶 in Henan.
For カイ, imagine a gathering of people in the ancient state all shouting 'Hi!' in unison: 'Hi' -> カイ, as they greet each other inside the city walls.
—