Needs a Better Title
Need a code name? Just pick a word appropriate to your abilities or temperament, add "O" to the end (or replace the end if that sounds better), and you're ready to go! This naming convention shows up a lot among superheroes.
Note that the rest of the character's name must be a significant word or variant of such. Rambo's name might end in O, but he is not an example of this trope.