Fruiz also known as Fruniz is a town and municipality located in the province of Biscay, in the autonomous community of Basque Country, northern Spain.
Fruiz is one of the place names of the Basque Country finished in -iz. Julio Caro Baroja defended that the names came from a proper name + the Latin suffix ``-icus``
In the Basque area called vasconavarra Caro Baroja considered that -oz,-ez and-iz suffixes applied to the place names in antiquity indicated that the site had been owned by the person whose name was attached to one of those suffixes, being able to trace their origin from the Middle Ages until the time of the Roman Empire.
In the case of Frúniz, Julio Caro Baroja proposed that the name could come from a hypothetical Furius - a Latin word. If it is added the -icus suffix to the Latin word we get the word Furicus. From a very similar latin Furunicus we could reconstruct the origin of the place-name Frúniz. Furunicus might also be a son of Furious.
Fruniz was established as the proper name of the village, and in the early nineteenth century it was change to Frúniz, after establishing the Royal Spanish Academy in 1763 which forced to use the Spanish accent. However, the name continued developing in the Basque language, losing the intervocalic -n-, a common phenomenon from ancient Basque, which makes the name end up like Fruiz. The current name of the town in Basque is Fruiz while the known name in Spain is Frúniz.