The actress and model recalled how her parents decided to name her after a friend's horse.
Decker told Vanity Fair: "My mum's best friend had a horse named Brooke, so my dad suggested 'Brooklyn' as a more formal version, and it just stuck and now I live in Brooklyn part-time, so go figure."
The 25-year-old, who married tennis player Andy Roddick in 2009, also reveals why she gave up modelling at the peak of her career.
She said: "The Sports Illustrated cover was the last thing I shot. That week, I told my agent, 'You know what, I really . . . I don't want to be a model anymore. I really want to do movies.' And I think he wanted to wring my neck at the moment."
Decker made her feature film debut in the 2011 comedy Just Go With It, which also starred Adam Sandler and Jennifer Aniston.
She recently filmed Battleship alongside Taylor Kitsch, Alexander Skarsgard and Rihanna.
Decker also revealed that her new film What to Expect When You're Expecting - featuring Jennifer Lopez, Rodrigo Santoro, Cameron Diaz, Chace Crawford, Elizabeth Banks, Harrison Ford, Anna Kendrick, Chris Rock and Joe Manganiello - has her thinking more seriously about starting her own family with 29-year-old Roddick.
She added: "I think that I'd like to try to be a superwoman and have kids and work, so we'll see if I can actually accomplish that. But, if we're talking dream scenario, that would probably be it."
What to Expect When You're Expecting opens this Friday (May 18) in the US and next Friday (May 25) in the UK.
Watch a trailer for What to Expect When You're Expecting below: