Here's why the term fits:
* Short and Round: Rabbits have short, stubby tails, unlike the long, bushy tails of other animals.
* Fluffy and Dense: The tail is covered in dense fur, making it appear round and fluffy.
* Bobbing Motion: When a rabbit is in motion, its tail often bobs back and forth, adding to the "bob" imagery.
So, the word "bob" in this context is more of an onomatopoeia, a word that mimics the sound or movement it describes. It's simply a word that captures the visual and movement characteristics of a rabbit's tail.