Space first, walls later
In current English, room does two jobs that sit beside each other without being the same job. Used without a plural, it is the extent available for a body or an action: room to sit down, not enough room in the bag. Used as a countable noun, it is an interior boxed off from the rest of a building: a kitchen, a bedroom, a waiting room. Figurative English still rides the first track. Room for doubt and room to negotiate name scope, not plaster and furniture.
That split is the later history of the word. The chamber sense is the newcomer. The space sense is the inherited one.
A native word, already old in Old English
The origin of the word room is not a borrowing from French or Latin. English inherited it from Old English rūm, in use before 1150. The older noun meant space and extent; enough space to act in; and, often, a fit occasion or a stretch of time. Anglo-Saxon glosses treat both local and temporal uses, and they also record unhindered opportunity: room to take spoils, room granted at a decisive moment in heroic verse. In the Old English Gospel of Luke, the same noun names the lack of space in the lodging house at Bethlehem. The point is capacity, not a numbered guest chamber.
Middle English kept a crowd of spellings — roum, rum, rome, romme — while the meanings stayed close to that older range: extension in two or three dimensions, a particular place, a span of time, the act of making way. The modern spelling settled later. The long vowel before m did not diphthongize in standard English the way the vowel of house did, which is why the everyday pronunciation keeps a close /u/ rather than a diphthong. Some northern dialects did take that further step; a Lancashire form with a diphthong is reported. That is a local outcome, not the main line.
Old English also used rūm as an adjective, wide or spacious, and had an adverb rumlice. Those uses faded. Roomy took over the adjectival work. An early modern coinage roomth, sufficient space, built with the same ending seen in warmth, is now obsolete.
From a Germanic adjective to a noun
Comparativists reconstruct a Proto-Germanic adjective *rūmaz, roomy or open, and a related neuter noun *rūmą, space. English continues the noun. Close kin are easy to name. German Raum still primarily means space rather than a walled chamber. Dutch ruim covers both spacious as an adjective and, as a noun, the hold of a ship. Old Norse rúm, Gothic rūms, Old Saxon and Old High German rūm stand in the same row. Swedish and Danish rum keep the family visible in the modern North Germanic languages.
The deeper Indo-European step is less tidy. One long-standing reconstruction, used in etymological handbooks and in the American Heritage tradition, links the Germanic forms to a root *reue- or *reuə-, to open, space. Possible relatives outside Germanic include Avestan ravah- for space, Latin rus for open country (the source of rural), Old Irish words for a plain, and Slavic terms for level ground such as Russian ravnina. Other handbooks prefer *(H)rewH-, to tear open, and some dictionaries mark the Indo-European ancestor as uncertain. The Germanic story is solid. The exact older shape, and whether Latin rus truly belongs, remains a matter of scholarly preference rather than a closed case.
Inside English the morphology is simple. There is no prefix to unpack. The noun is the old stem. Later English added transparent derivatives — roomy, roomful, roommate, rooming house — without changing the root. The nineteenth-century verb to room, to lodge, is only the chamber noun put to work as an intransitive, attested around 1817 to 1825. Rooming-house, a house that lets furnished apartments, is labeled in historical dictionaries as chiefly American by the late 1880s.
How open space became a cabin, then a house
For centuries the English word did not mean a boxed-in interior. Old English had other nouns for that, notably cofa, which survives in a shifted form as cove. The chamber sense of room shows up in Middle English first as a nautical use in the early fourteenth century: a cabin or compartment of a ship. Only around the mid-fifteenth century is it clearly applied to a partitioned part of a building. The Middle English record also files compartments of barns and stables under the same heading.
The narrowing is easy to follow. Once a particular portion of space is available as a sense, a ship’s section or a walled bay in a house is just a portion with edges. The older, unbounded sense did not die. Make room, clear a passage or yield space, is recorded from the late fourteenth to the mid-fifteenth century and still uses the inherited meaning. Hotel English later specialized the countable noun, but phrases such as no room to spare keep the older force.
Other senses came and went. Room could mean a designated post or office, and in whose room could mean in whose place, a use now archaic. By the early eighteenth century the countable noun could stand for the people assembled inside the space. Compounds followed the furniture of modern indoor life: room-temperature from 1879, room-service from 1913. Twentieth-century chat rooms recycled the chamber metaphor for a gathering that has no walls at all.
What German still keeps apart
German Raum is the cleanest reminder of where English started. A physicist’s Raum is space; a hotel’s Zimmer is a room with a door. English collapsed those two ideas into one short native word, after a nautical detour in the 1300s. Make room and room to spare still point past the wallpaper to the open extent the Germanic adjective named first.