On her birth certificate, her name was registered as Florian Cloud de Bounevialle Armstrong. Despite her birth name, she was known from childhood by the name that is famous now Dido. Dido has made it clear that "Dido" is now her real name and not simply a stage name or nickname. Her name derives from that of the mythical Queen of Carthage. As a child, she had to deal with its ambiguous and unusual nature, which led to her being bullied and even to her pretending to have an ordinary name. As she explains:
To be called one thing and christened another is actub68ally very confusing and annoying. It's one of the most irritating things that my parents did to me. Florian is a German man's name. That's just mean. To give your child a whole lot of odd names. They were all so embarrassing. I thought it was cruel to call me Dido and then expect me to just deal with it.

dont know

As listed in the legal records, her full birth name is just
Florian Cloud De Bounevialle Armstrong
. Some of the stories she tells in interviews make it clear that her mother called her Dido as a child (which she did not like btw). The fact that Dido is not her legal birth name does not really matter anyway, if her parents call her Dido, then Dido it is.
The original source of the name Dido is its use as a nickname for Elissa. (a queen of Carthage in Greco-Roman mythology). Prior to that usage Dido may have been the name of a pre-classical Greek goddess.
http://en.wikipedia.org/wiki/Dido

Dido is her REAL NAME. Did you not click on Trivia and read the quotations she's made?