A fight had broken out that led to the Arapaho chief being stabbed, and the Atsina chief was killed in retaliation. He found the boy on a Friday, which was the nexus of his name from that point forward.
A confrontation erupted that resulted in the Arapaho chief being stabbed, and the Atsina chief was killed in response. He discovered the boy on a Friday, which became the origin of his name from then on.