E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The membrane on the heads of some new-born infants, supposed to be a charm against death by drowning.
To be born with a caul was with the Romans tantamount to our phrase, To be born with a silver spoon in ones mouth, meaning born to good luck. M. Francisque-Michel, in his Philologie-Comparée, p. 83, 4, says: Calle, espèce de coiffure, est synonyme de coiffé, and quotes the proverb, Ste. Migorce! nous sommes nées coiffées. (La Comédie des Proverbes, act ii. 4.)