Isildur is a figure from J. R. R. Tolkien's The Lord of the Rings, the king who cut the One Ring from Sauron's hand but refused to destroy it in Mount Doom, a decision that shapes the whole story. That fateful refusal made his name shorthand online for someone who will not do the obvious right thing, and short shouted clips of the name spread through Lord of the Rings memes, edits and reaction videos. The sound endures because the single word carries centuries of fictional history, betrayal and dramatic irony in under two seconds.