Ursula is a Latin name meaning "little bear," from ursa, which makes it technically the most bear-appropriate name in the registry if you're working with a large, powerful dog and want the etymology to match the animal. The Disney villain reading is also very much live: Ursula the sea witch from The Little Mermaid is one of the franchise's most theatrical antagonists.
The Disney Villain Tradition
Pets named after Disney villains occupy a delightful subgenre of ironic pet naming. The cat who terrorizes the household gets Maleficent; the dog who steals food gets Ursula. The sea witch version of the name carries a specific energy: large, flamboyant, magnetic, impossible to ignore. An owner choosing Ursula for those reasons is paying the character a compliment.
The Bear Name Reading
"Little bear" as an etymology is particularly apt for large, powerful, somewhat ungainly dogs — Newfoundlands, Great Pyrenees, or any bear-shaped dog who moves with that specific lumbering confidence. The human name Ursula is genuinely rare in current baby naming, which gives the pet version clear air.
The Counter-Reading: A Heavy Name for a Small Dog
Ursula on a tiny dog is a completely valid ironic choice. The gap between the name's weight (etymological, cultural, physical) and a 5-pound Chihuahua is precisely the joke. Many owners find this gap sustainable indefinitely.