In the Late Empire and Middle Ages Vergilius was spelled Virgilius. Two explanations are commonly given for this alteration. One deduces a false etymology associated with the word virgo ("maiden" in Latin) due to Virgil's excessive, "maiden"-like modesty. Alternatively, some argue that Vergilius was altered to Virgilius by analogy with the Latin virga ("wand") due to the magical or prophetic powers attributed to Virgil in the Middle Ages (this explanation is found in only a handful of manuscripts, however, and was probably not widespread). In Norman schools (following the French practice), the habit was to anglicize Latin names by dropping their Latin endings, hence Virgil. In the 19th century, some German-trained classicists in the United States suggested modification to Vergil, as it is closer to his original name, and is also the traditional German spelling.[citation needed] Modern usage permits both, though the Oxford guide to style recommends Vergilius to avoid confusion with the 8th-century grammarian Virgilius Maro Grammaticus. Some post-Renaissance writers liked to affect the sobriquet "The Swan of Mantua".[citation needed]
What country was the Oxford guide to style written in?