The word entered English from Latin in the sixteenth century. Its earliest recorded use, in 1566, named the financial department of the papal Curia in Rome, the treasury that handled Vatican finances. It appeared in a Protestant pamphlet by John Barthlet, that criticised the Roman church.
It travelled directly from Latin, bypassing French. The same Latin root had already given Italian, Spanish and French their own related words several centuries earlier. Before Latin lay Greek, though the Greek origin is uncertain. For its first two centuries in English it was used to describe the Vatican treasury and in specialist architectural writing, the vaulted spaces of buildings.
In Latin it named a room defined by its ceiling, a vaulted or arched space where the curve above gave the room its character. Before Latin lay Greek, and before Greek possibly a Proto-Indo-European root meaning to vault or to arch, though the origin remains uncertain.
CHAMBER and COMRADE share the same Latin root as this word. CHAMBER came through Old French around 1200, naming any room or enclosed space. COMRADE came through Spanish and French, from camarada, meaning someone who shares a room or sleeping quarters. One names the space. The other names the person you share it with. Both trace back to the same Latin word for a vaulted room.
By the eighteenth century the word had acquired a new meaning, shortened from a longer Latin phrase meaning 'dark chamber'. Artists including Vermeer are believed to have used room-sized versions for decades to achieve a precise perspective in their paintings. And then in the 1840s the word was adopted to include a more compact sense. English coined this new sense and then exported it back to French, German and Italian, languages that had lived with the Latin root for centuries without ever using it this way.
