lotus, lotus root, arrowroot
藕 centers on the lotus plant, especially its edible root, and by extension arrowroot, another starchy root vegetable.
藕 combines 艹 (grass/plant) with 耦, which likely contributes the sound. The character refers to the lotus plant, particularly its root.
The grass radical 艹 sits above 耦, like a plant growing from the ground. Picture a lotus plant with its edible root hidden below.
For グウ, imagine a gooey lotus root being pulled from the mud: gooey -> グウ, and the sticky root matches the plant.