drēam

The Old English drēam meant 'joy, mirth, gladness, music, noise.' It did not mean a sleeping vision. The word for sleeping visions in Old English was swefn. When the Norse-speaking Danes settled in England during the ninth and tenth centuries, their word draumr (a sleeping vision, a dream) merged with the Old English drēam. The Norse meaning won. By Middle English, dream meant what it means now — a vision during sleep — and the original English meaning of joy and music was gone.

The Norse draumr comes from Proto-Germanic *draugmaz, possibly related to the Proto-Germanic *dreuganą (to deceive) — making a dream, etymologically, a deception. Sleep deceives you into seeing things that are not there. The word encodes skepticism about the sleeping mind's reliability. Dreams are, by name, lies.

The figurative meaning — dream as aspiration, ambition, hope — appeared in English by the fourteenth century. 'I have a dream' (Martin Luther King Jr., 1963) uses the word in its most powerful figurative sense: a vision of what could be, not a vision during sleep. The sleeping dream and the waking dream share nothing except the word and the idea of seeing something that is not yet real.

Modern neuroscience has shown that dreaming occurs primarily during REM sleep and involves the brain consolidating memories and processing emotions. The Old Norse speakers who gave English the word 'dream' were not far off — the brain during REM sleep is producing images that are not real. Draugmaz — the deceiver — was an accurate description.