hypnagogia

The brief transition between wakefulness and sleep we experience each night has been known by many names: the ‘borderland state’, the ‘half-dream state’, the ‘pre-dream condition’. Its technical name is the hypnagogic state and, along with dreaming, it is one of the most fascinating altered states of consciousness we can experience without the use of drugs

The term ‘hypnagogic’ was coined by the 19th-century French psychologist LF Alfred Maury, and is derived from two Greek words, Hypnos (sleep) and agogeus (guide, or leader). Some years after Maury, the psychical researcher FWH Myers coined a complimentary term, ‘hypnopompic’, to cover similar phenomena occurring as we wake from sleep. Some researchers are keen to split hairs, but in general there seems little difference between the material produced in either state, the main difference being which point of the sleep cycle investigators have chosen to observe.

Interesting stuff to know! There's much MUCH more interesting information HERE