to swim, to move freely, to rove
斿 centers on free, fluid movement: swimming, moving without restriction, or roving about. The meanings share the idea of unconstrained motion.
斿 is a rare character. It appears to combine 方 (direction, side) with a right-side element that may relate to movement or a flag, but the exact historical development is uncertain.
The left side 方 suggests a direction, and the right side looks like a person (子) moving under a flag. Imagine someone swimming freely, roving wherever they want, guided by a fluttering banner.
For ヨウ, picture a swimmer moving freely through the water, and think of the English word 'yo' as a casual call to move: 'Yo!' -> ヨウ, and the swimmer roves onward.