journey, chase away, let go, going, travel
徃 centers on movement along a path: going, traveling, or a journey. The senses of chasing away and letting go extend from the idea of sending something on its way.
徃 combines 彳 (movement) with 生, which likely contributed the sound and the idea of going forth or living movement. The exact historical development is uncertain.
The left side 彳 suggests a path or step, and the right side 生 suggests life or birth. Picture a living being setting out on a journey, moving forward and leaving things behind.
For オウ, imagine a traveler going on a journey and letting out a long 'Oh!' of awe at the open road: Oh -> オウ.