Why do Norwegian and Swedish sometimes use both a word and a noun ending to mark definiteness?

In Norwegian and Swedish, the use of both a preceding word and a noun suffix to mark definiteness is known as the "double definite" construction.1

This occurs when an adjective modifies a noun that is already definite. In these instances, the definite article is placed before the adjective, while the definite suffix is attached to the noun itself. For example, in the phrase det store huset ("the big house"), both the word det and the suffix -et function to indicate definiteness. This structure is a distinct feature of Norwegian and Swedish, whereas other Scandinavian languages like Danish and Icelandic do not employ this double marking; for instance, the equivalent in Danish is det store hus, where the suffix is omitted.1