What English speakers use it for
In current English, company is a crowded word. It names a business that sells goods or services, and, in law, an entity that can own property and sue or be sued. It also names the people you spend time with, visitors in the house, a troupe of actors, a ship's crew, a unit of firefighters, and a military unit of tens or a hundred soldiers, usually under a captain. The commercial sense is the one that fills newspapers. The social one is still the one you hear at the door: we have company.
Those uses look unrelated until the history is laid out. They are not separate coins. They are the same noun stretched across fellowship, a working band, and then a legal person.
A French loan in Middle English
English did not inherit this word from Old English. It borrowed it. Middle English wrote it as companye, compainie, and many nearby spellings, after Anglo-Norman and Old French compagnie, itself attested in a swarm of variants such as cumpaignie and compaynie. In French the noun already covered the state of being with others, recorded around 1050, a group of people around 1100, friendship, a gathering, and a body of soldiers. Anglo-Norman also used a shorter sibling, forms such as cumpaigne, for companionship and, by the fourteenth century, a mercantile society.
How early the word is in English depends on the witness. The Oxford English Dictionary's first citation is from before 1275, in the Proverbs of Alfred, a piece often dated in composition to about 1200. Other surveys, working from a slightly different set of dates, place English use in the mid-twelfth century. The disagreement is about manuscripts and dating, not about the source language.
The loan gradually crowded out native Old English words for a host or a band, including werod and gefer. That is a familiar pattern after the Norman Conquest: a French social and institutional vocabulary settling over Germanic everyday words.
The bread in the middle
The French group-noun sits on the same stem as companion. That word for a person comes from Late Latin companio, built from Latin com or con, meaning with or together, and panis, bread. The literal sense is a messmate: someone who shares the loaf. The bread word itself is traced to a Proto-Indo-European root meaning to feed. The prefix goes back to a root meaning beside or with.
The last step that produced French compagnie is disputed, and the dispute is worth stating plainly. One analysis treats the French noun as the word for a companion plus the suffix -ie, which makes an abstract of state or collectivity. Another traces both the -ie type and the shorter French form to medieval Latin companium or conpanium, a body of warriors, later recast as compagnia, already used for an alliance in Italian sources from the eleventh century, perhaps by taking a plural as a feminine singular. Dictionaries often reconstruct an unattested Vulgar Latin form as the missing link; it is a reconstruction, not a surviving text.
The personal Late Latin noun companio is first found in the Lex Salica, the sixth-century Frankish law code. A widely held view is that the Latin is a calque of a Germanic compound with the same meaning: a person with whom one shares bread. Gothic gahlaiba, from a word for loaf, is the usual comparison, and a West Germanic form with the same structure is sometimes reconstructed behind it. If that is right, a word that looks classically Latin is translating a Germanic table custom.
Related forms keep the same image across Romance: French compagnie and compagnon, along with the clipped copain, Italian compagnia, Spanish compañía, Portuguese companhia, Catalan companyia. German Kompanie and Dutch compagnie are later loans from Romance, not independent native words. English accompany belongs to the same family.
From a crowd to a charter
Early English uses point to a large group of people. By the late thirteenth century the noun also means companionship, the fact of consorting. Around 1300 it can mean persons associated with you in any way. Middle English also used it for sexual union, a sense that later dropped out.
The hinge is the late fourteenth century, when the word names people united to carry out something jointly. English applied it to trade guilds, the medieval companies that survive in London as livery bodies. Around 1400 it is also a military subdivision of a regiment. The later infantry company, often sixty to a hundred men under a captain, grows from that military use. A company of players is the same working-group idea on a stage. A ship's company is the crew taken as one body.
The commercial sense, a business association, is in place by the 1550s. From there the modern firm is a short step: partners, a legal name, then a corporation. The abbreviation co. dates from the 1670s, marking partners whose names do not appear in the title. Using company as a way of saying the rest of any group is eighteenth-century. Keep company, to consort, is recorded from the 1560s; bear company is older, from about 1300. The saying that two is company is attested from 1849; three is a crowd is one of several rival endings from the same decades.
None of these later senses invents a new etymology. They keep stretching the picture of people who share a table until the table is a guildhall, a payroll, or a parade ground.
What the loaf still explains
Company and companion are one story. A listed firm, a regiment, and a guest in the parlor all go back to eating bread with someone. The origin of the word company is not a boardroom. It is a shared loaf, and a Frankish law code that needed a word for the person across the table.