The word newb, is defined as a person with little or no experience in a any given game. "Cannon" may have first been used due to the cannon like sound of the actual gun, or the guns cannon like apearance.
The gun, as pertaining to the game include a 100 round magazine and poor accuracy, it levels the playing ground for may "newbies" since all they have to do in any given map, is get close enough to the opponent, and they can fire for virtually, as long as needed, is often found to be very, very frustrating to many of the more experienced players of the game.
2. Man i just cant win with any other un than the newb cannon.