Noobelkins can be referred to simply as an extension of the word "noob" and is to be used in cases where the word "noob" just isn't enough to express your feelings for the person or persons whom you are conversing with.
It's made from the word "noob" and the addition of "kins" commonly used for domestic pets such as dogs and cats, e.g. "Fluffykins".
When someone kills you on CSS while you are AFK and they post in the chat "owned, owned, owned!" you could say "Noobelkins..."