Viper's name was created when at a young age he began specialising in venomous weapons and poisons. His whole personality and being revolved around this specialisation, he was trained to create poison, to be as quiet and stealthy as a snake, and to kill with venom.
 
Viper was brought up not knowing what the right expression and emotion to project, his facial expression almost always stays the same, there is no fear in his eyes, there is no happiness in his smile, his voice monotone when he speaks. Viper is used to this, it's all he has known and it makes him better at his job, there is no attachment to others around him, and there is no fear of being killed at his job.