Let’s try not to laugh with this one.
The Spanish ending -illo is a common diminuitive, meaning a smaller version of something. A vecino is a neighbor; a vecinillo is the cute word that Flanders calls his neighbors in the Spanish translation of the Simpsons.
So: anus means anus. And anillo — the very common Spanish word meaning “ring” — is thus really just “little anus.”
Yes, in Spanish, a ring is just a small anus.