A post, a duty, and a room
In everyday English an office is a room, a suite, or a building where clerical and professional work is done. The same noun still names the post itself: people run for office, hold office, and leave office. A government unit can be an Office, as in a patent office or a foreign office. Older and more formal usage keeps a further layer. An office can be a function assigned to a person or a thing. In the plural, good offices are helpful acts done for someone else. Church English still uses the word for a prescribed service, including the Divine Office recited at the canonical hours.
The origin of the word office is easier to see in that older layer than in the furniture. Duty came first. The workplace sense is a later specialization of the same noun.
Borrowed, not inherited
English did not inherit the word from Old English. It is a medieval borrowing. Middle English office, also spelled offis, ofice, and several other ways, comes from Anglo-French and Old French ofice, already in use in the twelfth century for a function or a place and for divine service. Behind the French form stands Latin officium. Some modern dictionaries treat the English noun as a French loan only. Others allow a parallel pull straight from Latin as well. The disagreement is about the immediate channel, not about the source: the Latin noun supplies the meaning.
First English evidence belongs to the thirteenth century. One standard etymological account places the word in the middle of that century as a secular post in government or administration, an employment with duties attached. The Oxford English Dictionary’s earliest citation is later in the same period, around 1300, in a life of Thomas Becket. Treatments that give a range of 1200–1250 are describing that same arrival, not a separate event.
The native Old English word it partly displaced in religious use was had, a term for rank, condition, or holy orders. After the borrowing, English kept office for the post, the rite, and, later, the room.
What Latin put together
Classical officium covered a wide but coherent field: a service, a kindness, an obligatory duty, a function, business in the sense of one’s proper work, and ceremonial observance. Medieval Latin added the church service. Roman writers used the word both for what station required and for a courtesy owed to someone with a recognized claim. Cicero’s treatise De officiis made the moral sense famous: the duties of public and private life. A related late-Roman title, magister officiorum, named a palatine administrator; Middle English still knew a maister of the office in that historical sense.
The Latin form is usually explained as a contraction of opificium, literally a doing of work. That older compound is built from ops, genitive opis, meaning power, resources, or means, a word related to opus, work, plus the combining form of facere, to make or to do, with a noun-forming ending. The deeper reconstructions are the Indo-European roots *op-, to work or produce in abundance, and *dhe-, to set or put.
The contraction is a fact of form, not a clean match of sense. Opificium stayed close to constructive work and to opifex, a craftsman. Officium moved toward obligation, service, and function. Dictionaries that record the contraction also note the gap. English office therefore inherits a duty-word, not a workshop-word. A separate Latin noun, officina, meaning a workshop or place of manufacture, is the source of Spanish oficina and related workplace terms on the Continent. That is a sibling of officium, not the parent of the English noun.
How the meaning moved
The earliest English uses name a charge, not a desk. A person held an office in government, in a great household, or, from the later fourteenth century in a clearly ecclesiastical sense, in the church. Around 1300 the word also covered official employment in general and the prescribed order and form of church services. The sense of a government or civic department is in place by the mid-fifteenth century.
The physical workplace is a later, though still medieval, turn. Middle English already used office for a place where business was conducted. It also used the word for household work-rooms and outbuildings given over to domestic service: a hous of office, an office hous. Modern British English keeps a trace of that in the offices of a house, the kitchen, pantry, laundry, and similar working parts. The everyday sense of a clerical room or office building grew from that spatial shift. A separate, now dated slang use for a privy is recorded from 1727.
The abstract senses did not vanish when the room became dominant. Good offices remains a set phrase for helpful intervention, especially in diplomacy. To do the office of something, in formal prose, is still to perform its function. Liturgical English kept the daily office. Political English kept the post: office-holder is attested by 1818. Office furniture and office hours follow in the nineteenth century, once the workplace reading had become the default for most speakers. An office party, a gathering for the staff of a workplace, is twentieth-century.
Related English words joined the family by a slightly different route. Official, officer, officiate, and officious come from Latin officialis and its descendants, not from a new analysis of the English noun. They keep the old link between the post and the person who performs it.
What nearby languages kept
Romance languages preserve close relatives of the same Latin noun: French office, Italian ufficio, Spanish oficio, Portuguese ofício, Catalan ofici, Romanian oficiu. Irish oifig comes from Latin through Middle Irish oific. Spanish and Portuguese split the old field more visibly than English does. Oficio stays with duty, craft, or function; the ordinary word for a workplace is oficina, from officina. English folded both the charge and, later, the room into one form.
A lost Middle English phrase makes the original range plain. Late fourteenth-century writers used office of life for the state of being alive, a calque of Latin vite officio. That sense did not survive. It is a useful reminder that the word once named any function something was bound to perform, including the mere fact of living, long before it named a building with desks.