The phrase comes from J. R. R. Tolkien's 1937 novel The Hobbit, where the Elves of Rivendell greet Bilbo and the dwarves with a teasing, joyful song built around tra la la lally. Later stage, radio, animated and film adaptations kept the Elves' music as a marker of Rivendell's safety and strangeness compared with the dangers outside. Online, the short sung line survives on its own because it needs no context: listeners instantly hear old fantasy, good humour and a place untouched by urgency.