1. Roman law. A direction to an heir asking the heir as a matter of good faith to give some part of the inheritance, such as a particular object, or all the inheritance, to a third party. • A fideicommissum was a device to overcome some of the technicalities of the Roman will. Originally it created a mere moral obligation, but Augustus made it enforceable by legal process.
2. Roman & civil law. An arrangement similar to a trust by which a testator gave property to a person for the benefit of another who could not, by law, inherit property. • Over time, this device was used to tie up property for generations, and most civil jurisdictions now prohibit or limit it. For example, in Louisiana, an arrangement in which one person bequeaths property to a second with a charge to preserve it and, at death, to restore it to a third person is a prohibited fideicommissum. — Sometimes spelled fidei-commissum. Pl. fideicommissa.
“The many formalities with regard to the institution of heirs and the bequest of legacies, coupled with the fact that many persons, e.g. peregrini, were incapable of being instituted heirs, or of being given a legacy, led, in the late Republic, to testators leaving directions to their heirs in favour of given individuals, which, though not binding at law, they hoped their heirs would, in honour, feel bound to carry out. The beginning of fideicommissa, therefore, was very like the early practice with regard to trusts in English law, and, as in the case of trusts, a time came when trusts were made binding legally as well as morally…. For brevity, the fideicommissum will here be called ‘the trust’, the person upon whom it was imposed (fiduciarius) ‘the trustee’, and the person in whose favour it was imposed (fideicommissarius) ‘the beneficiary’.” R.W. Leage, Roman Private Law 252 (C.H. Ziegler ed., 2d ed. 1930).
