The Romans used to hang beads of red coral on the cradles and round the neck of infants, to “preserve and fasten their teeth,” and save them from “the falling sickness.” It was considered by soothsayers as a charm against lightning, whirlwind, shipwreck, and fire. Paracelsus says it should be worn round the neck of children as a preservative “against fits, sorcery, charms, and poison.” The coral bells are a Roman Catholic addition, the object being to frighten away evil spirits by their jingle.
“Coral is good to be hanged about the neck of children ... to preserve them from the falling sickness. It has also some special sympathy with nature, for the best coral ... will turn pale and wan if the party that wears it be sick, and it comes to its former colour again as they recover.” —Plat: Jewel-House of Art and Nature.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894