From Kook Science

Hypnagogia [hypnagogic] (from French: hypnagogique, from Greek: ὕπνος, húpnos, "sleep" + ἀγωγός, agōgós, "leading"; hence, "leading to sleep") is the state of consciousness that exists between wakefulness and sleep (as in a person falling asleep), the praedormitium (from Latin: prae- + dormitum, "before sleep") state, as opposed to hypnopompia, the state between sleep and wakefulness (as in a person awakening from sleep). It is a condition of half-sleep that is associated with hallucinatory visions and voices, sometimes described as "hypnagogic phantasms" (Archer, 1935) and "presomnal or anthypnic sensations" (Weygandt, 1948).