From the "what the hell were they thinking" file (via the New York Post):

In the most bizarre name change since Puff Daddy became P. Diddy, the Material Girl has adopted the ancient Hebrew name of Esther.

The pop queen, whose six-night stand at Madison Square Garden started last night, says she's spooked by the fact that her mom, who was also named Madonna, died at the age of 30, when the superstar-to-be was 5.

"My mother died when she was very young, of cancer, and I wanted to attach myself to an other name," Madonna, 45, told ABC News.

"This is in no way a negation of who my mother was. I wanted to attach myself to the energy of a different name."

While she hasn't yet asked her friends to use the new moniker, Madonna is apparently called Esther when she studies the ancient Jewish mystical practices of Kabbalah.

Update: Based on the not safe for work (NSFW) version of the story at this site the shift in names seems somewhat appropriate...