An oneironaut is simply another name for a dreamer. The word is derived from Greek. In Greek mythology, the Oneiroi (Όνειροι, Dreams) were, according to Hesiod, sons of Nyx (Night), and were brothers of Hypnos (Sleep), Thanatos (Death), Geras (Old Age) and other beings, all produced parthogenetically. Cicero follows this tradition, but describes the sons of Nyx as fathered by Erebus (Darkness).