The “K” in J.K. Rowling’s pen name stands for Kathleen.
Rowling was born Joanne Rowling and did not originally have a middle name. Her publisher asked her to use initials for the Harry Potter books, partly because a gender-neutral author name was thought likely to appeal to a broad readership. Rowling chose “K” in honor of her paternal grandmother, Kathleen.
The resulting byline, J.K. Rowling, became internationally recognized when Harry Potter and the Philosopher’s Stone was published in 1997. Rowling has also published under the separate pseudonym Robert Galbraith for her crime fiction.
The name is sometimes incorrectly expanded as “Joanne Kathleen Rowling,” as though Kathleen were her legal middle name. The letter honors her grandmother; it was adopted for the author name rather than reflecting a middle name given at birth.