A more thorough explanation:

Definition: Fideicommissum is a legal term that originated in Roman law. It refers to a direction given by a testator to an heir, asking them to give some part of the inheritance, such as a particular object or the entire inheritance, to a third party. It was a way to overcome some of the technicalities of the Roman will. Originally, it created a moral obligation, but later it became enforceable by legal process.

In civil law, fideicommissum is an arrangement similar to a trust, where a testator gives property to a person for the benefit of another who cannot inherit property by law. This device was used to tie up property for generations, but 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.

Examples:

• A wealthy man leaves his entire estate to his son, with a fideicommissum directing him to give a portion of it to his daughter after his death.
• A testator leaves his antique collection to his nephew, with a fideicommissum directing him to give a particular vase to his friend after his death.

These examples illustrate how a testator can use fideicommissum to direct their heirs to give a portion of their inheritance to a third party. It creates a moral obligation on the part of the heir to fulfill the testator's wishes, even though it may not be legally binding.