"I am already dead"
Deriving from Omae wa mou shindeiru, it is usually used unironically among friends. It is also a cry for help that will be laughed at as you circle into the depths of despair, leaving behind any sanity you possess.
Hank Williams Jr gave Waylon that nickname and it means "Old Number One" in Japanese.
He gave it to him after the recorded "The Conversation" because it was Waylon's way of telling Hank it was okay to sing his daddy's songs. It was at the same time that Waylon took him out on the road with him because Hank Jr was at a low point.
Waylon:
Well, if he was here right now Bocephus
Would he think that we were right?
Do you think he might?
Hank:
Don't you know he would Watasha
Be right here by our side