The Oscar winner and Hugh have known each other for years and she reveals when they first met, he was obsessed with the way she and her sibling, Antonia, chatted to one another in a language no one else could understand.
"We went to dinner at a place in London called The Ivy with his then-girlfriend Liz Hurley and my sister and just a huge bunch of people and we just kind of clicked," Kidman tells Wall Street Journal Magazine editor-in-chief Kristina O'Neill, "My sister and I were speaking our secret language and he was, like, fascinated because my sister and I have this language that we can speak so we can be understood in a crowd and nobody can understand us."
Nicole admits the sisters' style of communicating has come in handy.
The wife of country singer Keith Urban adds, "It is helpful, let me tell you. It was really helpful when we were, like, at parties and we had our boyfriends and stuff... we would be able to use our language and they'd all be like, 'What?' It's a really good tip for all the sisters out there."
Grant recently recalled meeting Kidman for the first time and recounted a similar story.
He told Entertainment Weekly, "What I remember most was that she was very nice, charming, but when she spoke to her sister, she spoke in a secret language."