Tim Bowen sheds some light on the origins and definition of the phrase to kick the bucket.

This is a colloquial expression for ‘to die’ and is often used in a fairly light-hearted way, usually to talk about the deaths of well-known public figures as opposed to close family members or friends. Some believe the origin of the expression goes back to the days when public executions were the norm for various crimes from theft to murder. Hanging was the preferred method of execution and trees were often used for this purpose. A rope would be attached to a strong branch and a noose placed around the victim’s neck. The victim would then be forced to stand on an upturned water bucket. This was then kicked away and the victim’s neck would be broken, causing, one would hope, instantaneous death.