As a Catholic 'Theory of Origin 3' makes a lot of sense.
Kick the bucket ~ From Wikipedia, the free encyclopedia
An excerpt from ~ http://en.wikipedia.org/wiki/Kick_the_bucket
To kick the bucket is an English idiom that is defined as "to die" in the Dictionary of the Vulgar Tongue (1785). It is considered a euphemistic, informal, or slang term. Its origin remains unclear, though there have been several theories.
Theory of Origin 1:
A common theory is that the idiom comes from a method of execution such as hanging, or perhaps suicide, in the Middle Ages. A noose is tied around the neck while standing on an overturned bucket. When the pail is kicked away, the victim is hanged.
Theory of Origin 2:
Another theory relates to the alternate definition of a bucket as a beam or yoke that can be used to hang or carry things on. The "bucket" may refer to the beam on which slaughtered pigs are suspended. The animals may struggle on the bucket, hence the expression. The word "bucket" still can be used today to refer to such a beam in the Norfolk dialect. It is thought that this definition came from the French word trébuchet or buque, meaning balance. William Shakespeare used the word in this sense in his play Henry IV Part II where he says: "Swifter then he that gibbets on the Brewers Bucket." — William Shakespeare, Henry IV Part II
Theory of Origin 3:
A third theory suggests that the origin of the phrase comes from the Catholic custom of holy-water buckets: After death, when a body had been laid out ... and ... the holy-water bucket was brought from the church and put at the feet of the corpse. When friend came to pray... they would sprinkle the body with holy water ... it is easy to see how such a saying as "kicking the bucket " came about. Many other explanations of this saying have been given by persons who are unacquainted with Catholic custom — The Right Reverend Abbot Horne, Relics of Popery
Theory of Origin 4:
A fourth suggests that the phrase comes from a children's game. The person who kicks the bucket loses the game.