broad, wide, spacious, vast
寬 centers on physical or metaphorical spaciousness: broad, wide, vast, and by extension, roomy or unrestrained.
寬 combines 宀 (roof) with a phonetic component historically related to 萈, suggesting a spacious dwelling. The modern Japanese simplified form is 寛.
Under a roof 宀, the lower part 萈 looks like a wide-open area with room to stretch. Imagine a vast hall where you can move freely.
For カン, picture a wide can rolling through a spacious room: can -> カン, and the can emphasizes the broad, open space.