A more thorough explanation:

Entailed interest is a legal term that refers to an interest in property that can only be passed down to lineal descendants. This means that the property cannot be sold or given away to anyone outside of the family line.

For example, if a father owns a piece of land with an entailed interest, he cannot sell it to someone outside of his family. Instead, the land will automatically pass down to his children and their children, and so on.

Entailed interest is often associated with the concept of a fee tail, which is a type of estate that limits the inheritance of property to a specific line of descendants. This type of interest was common in feudal societies, but it is less common today.