A rose by any other name might smell just as sweet, but you might not want to find out if its name were 'stinkflower'. Names have meanings and evoke certain thoughts and reactions through each individual's experience.
Usernames are no exception. What you choose for a username, from a cute/amusing quote they've spoken, or has been spoken about them, to a catchphrase associated with them, there are hundreds of possibilities. Your choice says something about what you think of them or how you choose to interpret them for play.
1. Post and share what your username comes from, or what it means.
2. If you want to, meta on how your username reflects your interpretation/style of play for your character (even multiple incarnations/AU accounts of the same character.)
3. Others post to yours with thoughts on your reasons/choice, and what they think or thought it shows for your interpretation/play of the character.
4. Have fun, don't use this as an excuse to start wank or argue about characterization! Every choice and interpretation is valid.