All citrus trees belong to the single genus Citrus and remain almost entirely interfertile. Different names have been given to the many varieties of the species. Italy for its peel, producing a primary essence for perfumes, also used to flavor Earl Grey the blood oranges. It is a hybrid of bitter orange x lemon.
Like the sweet orange, it is a pomelo x mandarin hybrid, but arose from a distinct hybridization event. It often serves as a rootstock for sweet orange trees and other Citrus cultivars. An enormous number of cultivars have, like the sweet orange, a mix of pomelo and mandarin ancestry. In several languages, the initial n present in earlier forms of the word dropped off because it may have been mistaken as part of an indefinite article ending in an n sound. This linguistic change is called juncture loss.
The color was named after the fruit, and the first recorded use of orange as a color name in English was in 1512. The sweet orange is not a wild fruit, having arisen in domestication from a cross between a non-pure mandarin orange and a hybrid pomelo that had a substantial mandarin component. In Europe, the Moors introduced the orange to the Iberian Peninsula which was known as Al-Andalus, with large scale cultivation starting in the 10th century as evidenced by complex irrigation techniques specifically adapted to support orange orchards. Spanish travelers introduced the sweet orange into the American continent.