The long ringlets of a lady's hair. Repentir is the French for a penitentiary, and les repentirs are the girls sent there for reformation. Repentir, therefore, is a Lock Hospital or Magdalen. Now, Mary Magdalen is represented to have had such long hair that she wiped off her tears therewith from the feet of Jesus. Hence, Magdalen curls would mean the long hair of a Mary Magdalen made into ringlets.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894