oar, scull, paddle
櫂 centers on a long, flat-bladed tool for propelling a boat: an oar, scull, or paddle.
櫂 combines 木 (tree/wood) with 翟, which likely contributes the sound and may relate to a bird's wing or feather, suggesting a wooden tool that moves like a wing through water.
The left side 木 is wood, and the right side 翟 looks like a bird with feathers. Imagine a wooden oar shaped like a bird's wing, slicing through the water.
For トウ, picture rowing a boat with a toe-shaped oar: toe -> トウ, and your wooden oar pushes the water.