The story
A conflation of two Biblical references: * Then I commended mirth, because a man hath no better thing under the sun, than to eat, and to drink, and to be merry * Let us eat and drink, for tomorrow we [shall] die A direct quote from the Book of Mormon: * Yea, and there shall be many which shall say: Eat, drink, and be merry, for tomorrow we die; and it shall be well with us.
Etymology from Wiktionary, CC BY-SA 4.0.