enclosure, quarter, red-light district
廓 centers on a defined, enclosed space: a walled enclosure, a distinct quarter within a city, or a designated red-light district. The common thread is a bounded area set apart from its surroundings.
廓 combines 广 (building or roof) with 郭, which itself means outer wall or enclosure. Together they reinforce the idea of a walled or roofed enclosure. The exact historical development of the combined form is not fully clear, but the component relationship is consistent with the meaning.
Under a roof (广), the inner part 郭 looks like a walled city quarter with a gate (⻏) and a watchtower (the top part). Picture a distinct, enclosed district within a city, like a red-light quarter, clearly marked off by walls and a roofed entrance.
For カク, imagine a walled enclosure with a big lock on the gate: the sound of the lock clicking shut is 'kaku'. The lock secures the quarter, and 'kaku' cues カク.