Why does the pen name J.K. Rowling include the letter K?

The K in J.K. Rowling honors her paternal grandmother, Kathleen.

Rowling was born Joanne Rowling, without a middle name. Before publication of Harry Potter and the Philosopher’s Stone, her publisher asked her to use two initials rather than her full first name. The marketing decision was intended to make the books appear less obviously written by a woman and, in the publisher’s view, to appeal to boy readers.

Rowling chose K for Kathleen, the name of her paternal grandmother. The resulting author name, J.K. Rowling, became one of the most recognizable pen names in modern publishing. It is not an abbreviation of “Joanne Kathleen” as a birth name.

The author later used other names for different kinds of writing. Her adult novel The Casual Vacancy was published under J.K. Rowling, while her detective fiction was written as Robert Galbraith. Those choices separated the Harry Potter identity from her later genres, but the original reason for the K remains her grandmother’s name.