A phrase invented by comedian Patton Oswald. Since many comedians have capitalized on their own catch phrases like "git-r-done" and "you know you're a redneck when" he decided to make up a meaningless phrase as his calling card. I have actually been hearing the phrase on the radio lately as a euphemism for having sex.
He was going on a date so I told him to put the puppy in the bucket.
The actual origin of the term is from England, and began in the later middle ages. A corpse would be laid out, and a bucket of holy water placed at its feet. Visitors could then sprinkle the deceased with Holy Water. Other explanations (suicide, execution) came later to explain an idiom, of which the origin of the term had ceased, mainly as a result of the English reformation.
"To Kick the Bucket" is explained by Bishop Abbot Horne in 1949, in his booklet "Relics of Popery" CatholicTruthSociety. He adds "Many other explanations of this saying have been given by persons who are unaquainted with Catholic Custom"
"My grandma died on May 12th of 2000. She was gonna try to hold off until May 17th, which was when my grandpa died, but ultimately she kicked the bucket."
-me