A tough guy or dangerous man. This goes back to the days of Gunsmoke, hayseeds, John Waynes and wild west saloons. Back when curly wolves were "reckoned with" instead of shot at by some punk with mommy and daddy issues.
Dead via GIPHY Will Smith - Fresh Prince of Bel Air
Ashes to ashes, dust to dust. When the soul and spirit of a man has moved on to the afterlife.
2.) When you are beat, dog tired. Life has done a number on your soul. 3.) When something has amused you, weaken you or has taken you out of your natural loving element of life. When you can't, just can't. "I'm dead."