Ring-fence

A ring-fence is an enclosure that completely surrounds an estate, a farm or a piece of ground. It is also used as a verb and first dates in this literal sense from the late 19th/ early 20th century. Since the 1980s, however, it is has been revived primarily as figurative business jargon, especially in financial contexts, meaning to separate funds, investments, businesses etc from others so that they can function independently.