Kick the Bucket
This evocative phrase meaning to die is of uncertain etymology. The most likely explanation is that it does not refer to a washing tub or pail, the sense of bucket that most of us are familiar with. Instead, it comes from another sense of bucket meaning a yoke or beam from which something can be hung. The imagery evoked by the phrase is that of an animal being hung up for slaughter, kicking the beam from which it is suspended in its death throes.
This sense of bucket probably comes from the Old French buquet, meaning a trébuchet or balance. The more familiar sense of pail is likely from the Old French buket, meaning a tub or pail.
Shakespeare describes this imagery of a slaughtered animal's death throes in Henry IV, Part 2 (III.ii.283):
Swifter then hee that gibbets on the Brewers Bucket.
The earliest known use of the phrase to kick the bucket is from Grose's 1785 Classical Dictionary of the Vulgar Tongue, where it is glossed as:
To kick the bucket. to die. He kicked the bucket one day; he died one day.
It is often suggested that the term refers to a hanging, where the hanged stands on a pail which is then kicked out from under him. There is no evidence to support this and it probably got its start as speculation attempting to make sense of the phrase long after the sense of bucket meaning beam was forgotten.
(Source: Oxford English Dictionary, 2nd Edition)