I'd go with good old Naughtius Maximus. Or Incontinentia Buttocks with female courier.
C.D. my first Legion run (who was a Lady) she would actually have a name given to her by Lanius. Probably Legate Juno, or Omnibus Sanctis, being that she would be the mother of the next leader of the Legion, and the mother of the new Mojave.
If the Courier is a woman, there are three honourary titles good old Caesar might possibly give to her as a token of her initiation into the Legion as its first known female soldier and agent.
1. Septimia Zenobia
Following her husband's death, Septimia Zenobia was the self appointed "queen" of Palmyra (the name given to Syria when it was still under Roman rule during the second and third centuries after Christ), who led an ambitious crusade against the rest of the Roman Empire in a series of successful skirmishes throughout the Middle East and Africa. She was successfully able to capture Egypt and portions of modern Turkey, before her soldiers were finally overwhelmed by Roman troops.
Although she was clearly an enemy of the Roman Empire, Caesar could very well name the Courier after Zenobia to symbolise her cunning and audacity as a warrior woman among her underestimating male peers.
2. Nike Of Samothrace
While it's the name of a Greek goddess, it's still an appropriate name that Caeser could bestow upon the Courier; Nike was the goddess of victory and protection. "Nike of Samothrace" is the name of an ancient sculpture that you can find today at the Louvre Museum; it's presumed that the sculpture was created by an artist known as Pythokritos to celebrate a naval war the Greeks were victorious in, which makes the name more than appropriate for the Courier (as the Battle of Hoover Dam takes place over water, as well).
3. Minerva
Although she was often associated with Nike and (of course) Athena, Minerva was the Roman goddess of wisdom and warfare. Certain cults compared her to the female equivalent of Mars (which is said to have caused some tension between both religious sects), so naming the Courier after Minerva would definitely mark her as Lanius' equal and counterpart. Naturally, I doubt Lanius would approve of this, though he'd probably comply with Caesar through gritted teeth.