In Japanese, the name Ryuu means-A dragon..The name Ryuu originated as an Japanese name. The name Ryuu is most often used as a boy name or male name.Japanese Name Meaning-A dragon.Origin-Japanese.n Japanese, the name Ryuu means-A dragon..The name Ryuu originated as an Japanese name. The name Ryuu is most often used as a boy name or male name. Japanese Name Meaning-A dragon. Origin-Japanese.