room, the wall of a house, man's name
廆 centers on a room or the wall of a house. The name usage is a specific application of that architectural idea.
廆 combines 广 (building enclosure) with 鬼, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a room or wall within a building.
Under a roof 广, a ghost 鬼 haunts a room, pressing against the walls of the house.
For カイ, imagine a ghost in the room whispering 'kai' like a spooky echo: kai -> カイ, and the ghost presses against the wall.