bend, curve, crooked, perverse, lean, forcibly, against one's will
枉 centers on deviation from a straight or proper path: physically bending or curving, and figuratively being crooked, perverse, or acting against one's will. The idea of forcing something or leaning away from the norm ties these senses together.
枉 combines 木 (tree/wood) with 王, which likely contributes the sound. The original idea may have been wood that is bent or not straight, but the exact historical development is uncertain.
A tree 木 beside a king 王: imagine the king leaning on the tree so heavily that it bends crookedly. The tree is forced into a curve against its natural will.
For オウ, picture the king bending the tree and saying 'Ow!' as it snaps crookedly: Ow -> オウ.