In Tamil, "Pasu" means cow. Kāmadhenu which is known to be a cow and is said to be good to give all sorts of wealth. During Kurma Avatharam taken by Lord Vishnu, all sorts of good things came out of it, which is useful to the world. One of those good things is Kāmadhenu, which is gifted to Indiran, the king of swargha Lokam.
Pasu (Cow)= Aa + than