helm
柂 centers on the helm of a ship, the steering mechanism that controls direction.
柂 combines 木 (wood) with 㐌, which likely contributes the sound. The character refers to a wooden helm or tiller used for steering a boat.
The left side is 木 (tree/wood), and the right side 㐌 looks like a steering mechanism. Picture a wooden helm made from a sturdy tree, used to steer a ship.
For イ, imagine an eagle (イーグル) perched on the wooden helm, guiding the ship: eagle -> イ.