Right you are LH. From Wiki:

Lady Gaga was born Stefani Joanne Angelina Germanotta.

Music producer Rob Fusari, who helped her write some of her earlier songs, compared some of her vocal harmonies to that of Freddie Mercury. Fusari helped create the moniker Gaga, after the Queen song "Radio Ga Ga". Gaga was in the process of trying to come up with a stage name when she received a text message from Fusari that read "Lady Gaga." He explained,

Every day, when Stef came to the studio, instead of saying hello, I would start singing 'Radio Ga Ga'. That was her entrance song. [Lady Gaga] was actually a glitch; I typed 'Radio Ga Ga' in a text and it did an autocorrect so somehow 'Radio' got changed to 'Lady'. She texted me back, "That's it." After that day, she was Lady Gaga. She's like, "Don't ever call me Stefani again."