The first written reference to Picu Urriellu as Naranjo de Bulnes is credited to the German geologist and engineer, Wilhelm Schulz, who, in 1855, published the first topographic and geological map of Asturias. As far as is known the etymology of this name is not clear, because, historically, the local inhabitants always referred to the mountain as Picu Urriellu. It has been suggested that the name can be attributed to the orange hue of the limestone from which the peak is formed. The local residents of Bulnes have a saying concerning the contentious name: No me llameis Naranjo, pues fruto no puedo dar, llamadme Picu Urriellu que es mi nombre natural. (Don't call me Orange tree, because fruit I cannot bear, call me Picu Urriellu which is my natural name).