The uni department I worked at once had a student called "Daniel". He was on a engineering scholarship from somewhere in remote Africa and had never needed another name. He was rather rueful that nobody had told him to make one up when he applied for his passport, because it caused him all kinds of difficulty. He was all kinds of things on different bits of paper: "Daniel Daniel", "Daniel -" and, memorably, "Daniel Dash".
Grew up somewhere in Indonesia (I think) and never got a last name. So they just duplicated his first name.