The line comes from The Lord of the Rings: The Fellowship of the Ring, released in 2001 and directed by Peter Jackson. Gandalf, played by Ian McKellen, confronts the Balrog in Moria and holds the Bridge of Khazad-dûm so the Fellowship can escape. Although the book uses a slightly different phrasing, the film version became the quoted form online. It spread through forums, reaction videos and meme edits as a universal way to refuse entry, and remains popular because the delivery is instantly recognisable and easy to reuse.