My friend Angela mentioned that when she was confirmed she was told "We no longer take names for confirmation." So Angela took her name 'secretly' - she can do that. When I was confirmed, it was a very big deal to take a name; in fact, part of our retreat before confirmation dealt with our discerning which name to take. When my little brother was confirmed eleven years later, he wanted to take the name of a movie star he liked. I took care of that - after we prayed to the Holy Spirit, I made him draw a saint's name and that is the name he got.
Sr. Mary Martha has a fun and informative post on the subject. One thing she says is that our confirmation name will be our name in Heaven - so I guess I'll be called St. Peter... Be nice to me - you may have to deal with me at the gates. (All of us Peters stick together, you know.)
[Art: "The martyrdom of St. Peter of Verona" I am named after this St. Peter.]