Cannot change user name in Trello

[Bernard Claviere -Croisade pour la santé-]

Hi there.
I have managed to change the Full name, the Initials, but when I try to change the User name, I am told it is already in use, whatever the user name I enter.
Obviously, the whole dictionnary is not registered as user names... 

:)

Many thanx

[marc -Collabello--Phase Locked-]

Basically, the Trello user is a unique string of characters.  Trello assigns this user name, and surprisingly many names are already used (or were in use earlier).

Why do you want to change the user name?

[Bernard Claviere -Croisade pour la santé-]

Hi Marc. Many thanx for your answer.

I do not quite understand what you mean, but it does not matter. 
I don't see how Trello could have created 'out of nowhere' so many user names like the ones I'm trying to register.
Anyway... 
I want to change my user name because I do not identify with the one I first registered a long time ago. I"d prefer one that fits me better, specially now that I work with a team whose members are naturally tempted to ask "why did you chose that name"? 

Do you see a solution for me ?