Why do people say "kick the bucket"?

Most people are familiar with the expression “kicked the bucket,” which is used as a humorous euphemism for “died,” but no one we spoke to was quite sure where it originated.

Common Phrases and Where They Come From by John Mordock and Myron Korach had a few guesses, both fairly gruesome. They say the phrase may have come from the days of execution by hanging, when the executioner would kick the bucket out from under their victim’s feet. It’s also possible that the idiom originated in the slaughterhouse, where livestock would sometimes kick a literal bucket as they died.

For the curious, Marvin Rubenstein’s American English Compendium has more information on English slang, sayings, and acronyms, including a section comparing British and American English.