What's in a name?

Vergil or Virgil? Which is correct?

Vergil's full name was Publius Vergilius Maro... so where did 'Virgil' come from? Professor William Harris offers some possibilities in his essay on The Secret Life of a Very Private Poet:

Donatus adds that Vergil was so pure in life, in speech and in spirit, that he was nicknamed "Parthenias" or "The Maiden" at Naples, where he habitually lived. (One thinks of "virgo", and the variant spelling of the name Virgilius, perhaps stemming from his mother's dream that she would bring forth a "rod" or virga.....)

One is certainly tempted to make the connection between Virgil and the Latin virgo, virginis m. (maiden, virgin)... (Harris continues to discuss possibilities for the origin of his nickname Parthenias.)

On this topic, N. S. Gill notes:

According to Gilbert Highet in The Classical Tradition, the misspelling (Virgil) began early, possibly as the result of Vergil's nickname Parthenias which was based on the poet's sexual restraint. In the Middle Ages the name Virgil was thought to refer to his magical (as in the virga magic wand) powers.

Thus, considered a wizard (and prophet) in medieval times, the alternate spelling may stem from the connection with virga, -ae f. (a rod, wand, broom).

(...then again, maybe someone just misspelled his name along the way, and it caught on...)