Codename

By 1997, some skywatchers believed that the Brigadier was a UNIT codename, likening it to their scientific advisor, the Doctor. (PROSE: The Dying Days)

'Damsel, as in "damsel in distress", was River Song's codename for the Doctor, owing to the fact that he "needed rescuing a lot" of the time. (TV: The Husbands of River Song)