Passage: The development of Cortana started in 2009 in the Microsoft Speech products team with general manager Zig Serafin and Chief Scientist Larry Heck. Heck and Serafin established the vision, mission, and long-range plan for Microsoft's digital-personal-assistant and they built a team with the expertise to create the initial prototypes for Cortana. Some of the key researchers in these early efforts included Microsoft Research researchers Dilek Hakkani-Tür, Gokhan Tur, Andreas Stolcke, and Malcolm Slaney. research software developer Madhu Chinthakunta, and user-experience designer Lisa Stifelman. To develop the Cortana digital assistant, the team interviewed human personal assistants. These interviews inspired a number of unique features in Cortana, including the assistant's "notebook" feature. Originally Cortana was only meant to be a codename, but a petition on Windows Phone's UserVoice site that proved to be popular made the codename official.

Question: What action led to Cortana being the official name?
a petition