kick the can? or the bucket?

A couple of nights ago Rob, Carter and I were watching the bucket list. Carter was sorta zoning in and out as he was building one of his new Lego sets. He was laying on the floor when he piped up, "what are y'all watching?" Rob told him it was the bucket list. Carter asked him why it was called the bucket list, and Rob explained that it's a list someone makes of all the things they want to do before they "kick the bucket". Carter pondered that for a moment and then said questioningly "what bucket do they kick? and why do they make a list for it?"