How did siting bull get his name?

Answer 1

As an infant he was named "Slow" by his father, Returns Again.

Both father and son had special relationships with animals, often seeming to converse with wild creatures in some strange language. One time when out hunting for buffalo, Returns Again and three companions were sitting near their evening campfire when they heard an odd sound in the darkness, a sound that seemed to be drawing nearer.

It was a solitary buffalo bull and instead of fearing the fire it appeared to want to come close, muttering sounds as it did so. Returns Again made out four Lakota names being repeated by the bull: Sitting Bull (tatanka iyotake), Jumping Bull, Bull Standing and Lone Bull. None of the other hunters understood the sounds, but Returns Again was certain he had heard correctly and that the buffalo was offering him a choice of four new names for his son.

Returns Again chose the first one: Sitting Bull.

For the Lakota, the buffalo was not only a source of shelter and food (and many other commodities), but it also represented a sacred buffalo spirit creature and was revered as Holy. To be given a name by a buffalo bull in those circumstances was a religious experience unlike most others.