J.K. Rowling’s original surname was Rowling.
She was born Joanne Rowling, and “Rowling” was her family name before she married Portuguese television journalist Jorge Arantes in 1992. After the marriage she was sometimes known as Joanne Rowling Arantes. She later married Neil Murray in 2001 and has also been referred to as Joanne Murray.
Her publishing name remained J.K. Rowling. The initials were selected before the first Harry Potter book appeared, when her publisher wanted a name that did not immediately identify the author as a woman. Rowling supplied Kathleen, the name of her paternal grandmother, for the middle initial.
The surname is often confused with the name “Rowling” as a shortened form of “rolling,” but it is the family name she was born with. “K. Rowling” is therefore not her original full name; it is the public author name created for publication.