The term eruv is a shortening of eruv chatzeros (עירוב חצרות‎‎), literally a "merger of [different] domains" (into a single domain). This makes carrying within the area enclosed by the eruv no different from carrying within a single private domain (such as a house owned by a single person), which is permitted.

The eruv typically includes numerous private homes, as well as a semi-public courtyard whose ownership is shared by them. To enact the merger of the homes and courtyard into a single domain, all home owners as well as owners of the courtyard must pool together certain foodstuffs, which grants the area of the eruv the status of a single private domain. As a precondition for this merger, the area must be surrounded by a wall or fence.