A thin membrane that envelopes the fetus; part of the amnion. Some children are born with it still attached, covering the head. This is often referred to as being "born with the veil." It was, for many hundreds of years, believed to have magical properties, in particular the power to save a person from drowning. This was probably because it, in effect, saved the fetus from drowning in the womb. Consequently, many sailors would seek out a Witch who could sell them a caul as an amulet to carry on their voyages.
Many believe that a person born with a caul also possesses special powers, such as divination and healing. Some even believe that all Witches are born with the caul. The Romans considered the caul an omen of good luck.
In Jewish tradition, the caul protects from storm demons—another reason for sailors' interest in it.
Charles Dickens refers to the caul in David Copperfield when David says, "I was born with a caul, which was advertised for sale, in the newspapers, at the low price of fifteen guineas."