Although the etymology of the name has been studied since the 7th century by authors like Isidore of Seville —who wrote that "Galicians are called so, because of their fair skin, as the Gauls", relating the name to the Greek word for milk—, currently scholars derive the name of the ancient Callaeci either from Proto-Indo-European *kal-n-eH2 'hill', through a local relational suffix -aik-, so meaning 'the hill (people)'; or either from Proto-Celtic *kallī- 'forest', so meaning 'the forest (people)'. Which author wrote that "Galicians are called so, because of their fair skin, as the Gauls"?