wood streaks
橒 centers on the visible grain or streaks found in wood, referring to the natural linear patterns in timber.
橒 combines 木 (tree/wood) with 雲 (cloud), likely as a phono-semantic compound where 雲 provides the sound and the cloud-like pattern suggests the streaked grain of wood.
The left side is a tree 木, and the right side is a cloud 雲. Picture the swirling, streaky shapes of clouds mirrored in the grain of a wooden plank: 橒 is wood streaks.
For ウン, imagine a woodworker saying 'Ooh, look at those wood streaks!' The 'Ooh' sound cues ウン while admiring the grain.