donkey
驢 centers on the donkey as an animal, specifically a beast of burden related to horses.
驢 combines 馬 (horse) with 盧, which likely contributes the sound, to form a character for donkey, an equine animal.
The left side is a horse 馬, and the right side 盧 looks like a complex stable. Picture a donkey standing beside the horse stable, a smaller but sturdy equine.
For ロ, imagine a donkey braying a low, rolling sound: rooo -> ロ, like the donkey's call echoing from the stable.