Tacitus and other Roman sources report that Queen Boudicca of the Iceni had two daughters, whose names remain unknown. It is generally agreed that their rape by Roman soldiers was one of the events that spurred the Iceni people into open revolt. Popular tradition has the daughters accompanying their mother into battle and dying beside her. Lesser-known traditions have one or both of the daughters being sent away before the battle to a remote British region, beyond Roman reach.
For his 1598 play Boudicca, William Shakespeare fictionalised the title character's daughters with the names Epona and Bonvica. In the play, the sisters accompanied their mother into the battle against the Romans. When it became apparent that their cause was lost, Epona threw herself from a ledge rather than be captured by Suetonius. Bonvica then chose to drink poison with her mother, who let her daughter have a greater dose so as to ensure a quicker death.
The name Epona for the older daughter comes from John Fletcher's play Bonduca. Fletcher left the younger daughter unnamed, so Harry Turtledove chose Bonvica himself.