Hypnagogic: Concerning the drowsiness one commonly feels before sleep, the transitional state preceding sleep, and also the hallucinations that may occur at that time.
The original French word "hypnagogique" was derived from Greek roots "hypno-", sleep + "agogos", leading = leading to sleep. In the 19th century "hypnagogique" came across the English Channel and became "hypnagogic."
A closely allied term is "hypnoidal." It means resembling hypnosis and also refers to the subwaking state, the condition intermediate between sleeping and waking.