Night pictures and waking hopes
In present-day English, a dream is first of all the stream of images, feelings, and half-stories that occupies the mind in sleep. The same noun also names a waking reverie, a private ambition, and, in casual speech, anything so pleasant it barely seems real. The verb tracks those senses: people dream at night, dream of another life, and dream up schemes that did not exist an hour earlier. None of that range is obvious from the word’s earliest English life.
What Old English actually recorded
Old English already had the form, written drēam. In the texts that survive, it does not mean a vision during sleep. It means joy, noisy merriment, and music: public sound and celebration, not the private theater of the night. When writers needed the sleep-vision, they reached for other nouns. The usual one was swefn, a member of a large Indo-European family of sleep-words. Mæting and gesihð appear as well.
The sleeping-vision sense is first solidly attested in the middle of the thirteenth century, in Middle English spellings such as drem. Around the same time the old festive meaning thins out, and the Old English verb that went with it — West Saxon dryman, Anglian drēman, to sing, rejoice, or make music — drops out of use by about 1300. A new verb, dremen, is built from the noun in its nocturnal sense.
One word, two words, or a northern loan
Whether the joy-noun and the sleep-noun are historically the same item is still an open question. Some etymologists treat them as homonyms that collided in spelling. Others suggest that a sleep meaning of drēam existed in speech but was kept out of literature because the festive word already filled the slot, so scribes preferred swefn. A third line of argument, and the one that pays closest attention to geography, is that the sleep sense was reinforced, or even brought in, by Old Norse draumr after Scandinavian settlement in Britain.
That last account has distributional support. In Middle English, dream taking over from sweven is earliest and most frequent in the East Midlands and the North, the areas of heaviest Norse contact. The Oxford English Dictionary still marks the sleep-noun as uncertain: either the reflex of an unattested Old English cognate of the continental dream-words, or a borrowing from early Scandinavian whose vowel was later remodeled on native lookalikes such as stream, seam, and team.
The origin of the word dream, then, is not a single clean inheritance. It is a fork that dictionaries have not closed.
A reconstructed Germanic noun
On the continent the sleep meaning is the normal one. German Traum, Dutch droom, Old High German troum, Old Frisian drām, Icelandic draumur, Swedish dröm, and Danish drøm all support a reconstructed Proto-Germanic masculine draumaz. That form is usually derived from an earlier draugmaz, with a nasal suffix on a root that also gives Old High German triogan and modern German trügen, to deceive, and Old Norse draugr, a ghost or walking dead. Outside Germanic, Sanskrit druh- (seek to harm) and Avestan terms for deceit are often listed as relatives, from a Proto-Indo-European root reconstructed as dhreugh.
The attractive story is that a night vision was named as an illusion, a mental trick. The reconstruction of the Germanic noun is widely shared; the leap from deceive to sleep vision is not. Critics note that many early cultures treated dreams as visitations or omens, not as lies, so a deception-etymology may be projecting a later attitude backward.
Old Saxon sits awkwardly between the English split and the continental sleep-word. Its drōm is recorded both as bustle, revelry, and jubilation and as a dream in sleep. That combination is the closest Germanic analogue to English, and it is why some dictionaries can still derive the modern English noun from Old English drēam in the sense of joy and music, merely noting kinship with Old Saxon drōm in both the festive and the nocturnal senses, without insisting on a Norse loan.
The verb in the sleep sense is a later formation from the noun, with a wide Germanic family of its own: Dutch dromen, German träumen, Swedish drömma, Danish drømme, Icelandic dreyma. Those forms track the continental sleep-noun, not the lost English sense of making music.
How the later senses arrived
Once the sleep meaning was established in English, the rest of the modern range grew by metaphor, not by a second borrowing. By the 1580s the noun could name what the imagination presents even while a person is awake. Late in the nineteenth century it could mean something of dream-like charm or beauty; by the early 1930s it could mean an ideal or an aspiration. Compounds such as dream girl are already mid-nineteenth-century. The verb picked up an idle, fanciful sense by the late fourteenth century. Dream up, in the sense invent in the mind, is a twentieth-century development.
The older native sleep-noun did not vanish at once. Sweven remained a Middle English competitor, then receded as dream spread from the North and Midlands. Romance languages took another road: French songe, Spanish sueño, and Italian sogno go back to Latin somnium, itself from the same sleep-root that gave Old English swefn and Greek hypnos. English is unusual in having abandoned that inherited sleep-noun as the name of the vision.
A northern fact worth keeping
If a tidy family tree is unavailable, a local fact still is. German Traum never had to share its form with a common word for music. English did, and the resulting gap in the Old English record is why the sleep sense surfaces so late on the page. The earliest Middle English evidence for that sense is thickest where Norse and English mixed. That northern clustering is the most concrete clue the word still offers.