Nicole Kidman and Keith Urban named their first daughter Sunday because it was their least favourite day of the week until they found each other.

The Hollywood actress gave birth to Sunday Rose, her first child with her country star husband, in 2008 and they subsequently welcomed a second girl, Faith, via a surrogate mother in 2010.

The couple revealed they called their youngest daughter Faith to reflect their long struggle with fertility problems, and now Urban has revealed the meaning behind Sunday's unusual name.

He says, "For me, Sunday used to be the loneliest day of the week because nobody's hanging out on a Sunday. They're all with their families and I used to dread Sundays. But when I met Nic, it became my favourite day of the week because we always spent it together. Nic had the same feeling so we said that if we had a child, we should call her Sunday."