A fideicommissum is a type of bequest in which the beneficiary is encumbered to convey parts of the decedent's estate to someone else. For example, if a father leaves the family house to his firstborn, on condition that they will bequeath it to their first child. It was one of the most popular legal institutions in ancient Roman law for several centuries. The word is a conjunction of the Latin words fides (trust) and committere (to commit), and thus denotes that something is committed to one's trust.