When Arabs conquered the island, Sicily was divided into three Districts: the “Val Demone”, the “Val di Mazara” and the “Val di Noto”. This division was preserved until 1812.
The name of the Val Demone referred to the northeastern part of Sicily and included the current province of Messina with Cefalù (west) and the territory of Troina (south) and Nicosia up to Catania.
The etymologic origin of the word “vallum” should go back to an Arabic term, wālī, which means “governor” or “viceroy”, the magistrates in charge of the provinces.
In the historian Michele Amari’s opinion, “vallis” is the translation in Latin of the word ʾiqlīm that indicates the territory, therefore it can also be used to indicate district and province.
In regards to the origin of the term “Vallo”, there are many opinions: some identify its origin with a castling of the IX century, abandoned during XII century, the ancient Dèmona or Demenna, others, from the greek-byzantine, with the verb "διαμένω" (“persist”, “endure”), because Dèmone was the only vallum that maintained Christian belief and resisted to Islamic incursions.