Credit: Jon Kopaloff/FilmMagic

Gwyneth Paltrow has quite a potty mouth.

When the 38-year-old actress stopped by E!'s Chelsea Lately on Monday, the Oscar winner proved she's not as prim and proper as she sometimes seems.

Host Chelsea Handler got the ball rolling when she discovered that they both call their grandmothers "Mutti" (the German word for "Mommy"). "My Mutti was a real bitch," Handler, 36, quipped.

Without missing a a beat, Paltrow replied: "My Mutti was a real c**t!"

"She just hated my guts, basically," Paltrow explained. "She tried to poison my mother against me, but it didn't work because I have a great mother [Blythe Danner, 68]. She was just tough."

"You look back and you think she must not have been very happy and she must have had a lot of pain, because she was mean as hell," the actress added.

Fortunately, Danner is a much nicer grandmother to Paltrow's two children, Apple, 6, and Moses, 5.

"She was adamant that she did not want to be called grandma. And who can blame her? My mom's hot and she didn't want to be called grandma," Paltrow laughed. "She decided she was going to be called 'Woof.' So she kept trying to make the 'Woof' thing stick. It's even her email address!"

"Apple just wasn't having it and one day she was just like, 'Lalo!' And that was it," Paltrow said. "She's Lalo."