Laetitia (レティシア, Reteishia) is the third persona of the former Margaret Burton and her memory keeper, who is unable to leave the Sanctuary behind the Door of Truth. The name "Laetitia" originally belonged to Margaret's favorite doll, and Madlax later used a forged Nafrecian passport with the name "Laetitia Luna" in it. According to Shigeru Kitayama, this character was named after the protagonist of the French film Les Aventuriers (1967, IMDb), which Kōichi Mashimo is particularly fond of, rather than after the Roman goddess of gaiety.

Source: Wikipedia