The Arbiter is one of the biggest characters that everyone loves like John 117. He gets his name from his failure to protect the first Halo Ring that the Master Chief known as John 117 had been destroyed in Halo Combat Evolved. As his original name is Thel Vadam, we all originally know him as the Arbiter. His armor gives him this name and it is supposed to bring great shame to his family and it means as he is banished from all groups.
The meaning of Arbiter is said to be a disgrace or some one who rebels and disobeys rule. The one big thing that it could mean a higher ranking even know the model of armor is out of its date compared to competing newer models.