Metal Jacket's name is a portmanteau and pun derived from two words. A bullet-vest and a yellowjacket respectively.
This name refers to his experience with deadly firearms as a result of activity in the Peace Division, his viciousness in combat, and his wasp-like appearance.
He gained this name after his Lord remarked that "He stings like a wasp". This would later inspire his choice of Vernacular ID later on in his military career.

• One of Metal Jacket's previous goals was to reform PentaCorp's Peace Division, as ironically it propagated more vitriol in the world than it did peace, which was something that Metal Jacket wanted to change.

• In all his years alive on the Earth, Metal Jacket always felt a kinship with Dreadnaught.
  They first met in the Peace Academy as Metal Jacket walked to Room P-12 and Dreadnaught walked to Room I-10, in which they would express themselves to each other. Metal Jacket would tell his new acquaintance how they would help the world and the people within it. In contrast to this, Dreadnaught would confide his doubts about the Peace Division to Metal Jacket, expressing confusion on how they were to deliver peace to the world by bringing war.
  At first, Metal Jacket brushed aside this question, as he claimed that while the means to achieve peace were sometimes violent, that it was a necessary compromise and that this only happened to those that deserved it.

• Metal Jacket's relationship with Io has gone through many ups and highs: the high moments being some of the greatest he's experienced in regards to his memories with other people and the low points making sinking Metal Jacket to the lowest moments of his life.
  Metal Jacket would first meet Io when his faith in the Peace Division had begun to weign, and in search for another way he would reach out to Dreadnaught