A membrane which sometimes covered the head of a child at birth. It was once thought of as a preservative against drowning in the sea, so consequently the caul was sought after by seamen.

Superstitions surrounding the caul reaches back into antiquity. In ancient Rome, Aelius Lampridius, wrote about the life of Antonine Diadumeninus saying he was so called from being born into the world with a band of membrane round his forehead in the shape of a diadem, and he enjoyed a perpetual state of felicity from this circumstance. Also, Roman midwives sold cauls by the Forum.

Even as late as the 1870s British newspapers often printed advertisements by prospective would be purchasers of a caul offering large amounts of money. The caul was used for divination. (See AmniomancyA.G.H.

Source: 9.