J.K. Rowling added the letter K to honor her grandmother Kathleen.
Rowling was born Joanne Rowling and did not have a middle name. Before the first Harry Potter book was published, her publisher asked her to use initials rather than her full first name. The intention was to make the author’s gender less obvious to potential readers, particularly boys.
Rowling chose “K” for Kathleen, the name of her paternal grandmother. This produced the professional name J.K. Rowling, although Kathleen was not part of Rowling’s legal birth name. The author has sometimes been incorrectly described as having been born Joanne Kathleen Rowling.
The initials became one of the most recognizable author names in modern publishing. Rowling later used the separate pseudonym Robert Galbraith for her Cormoran Strike crime novels, showing that her author identity has varied according to genre and publishing context.