oar, tower
艪 centers on a long oar or scull used to propel a boat, and by extension a tower-like structure, likely from the shape of a raised oar or a lookout on a boat.
艪 combines 舟 (boat) with 魯, which likely contributes the sound ロ. The character originally referred to a type of oar or scull used on boats.
A boat 舟 with a complex right side 魯 that looks like a tall oar standing up: imagine a long oar used to row, which can also resemble a tower when raised.
For ロ, picture a row of oars on a boat: row -> ロ, and each oar is a 艪.