Why rack your brains to come up with something original? It's as simple as that. You take your forum ID and that's it - your nickname is ready. Here you have both simplicity and originality. Imagine for a moment that our whole forum consists of such nicknames 
At least there would be no imposters on the forum 
My User ID is 553628
At least there would be no imposters on the forum My User ID is 553628
Thanks for mentioning my name, even though it's not super clever. It's definitely unique though.