Nomen nescio
Nomen nescio (pronounced [ˈnoːmɛn ˈnɛskɪ.oː]), abbreviated to N.N., is used to signify an anonymous or unnamed person. From Latin nomen – "name", and nescio – "I do not know", it literally means "I do not know the name". The generic name Numerius Negidius used in Roman times was chosen partly because it shared initials with this phrase.