Naming Day

Naming Day is one of the few known Matoran holidays. As the chief aspect of the celebration, specifically honored Matoran were recognized with a grant of a change in form to their names. The only known naming day was after the Bohrok crisis as a reward for the Matoran who did much during the crisis.

Name Changes
During the Naming Day after the Bohrok Crisis, four Matoran and a Ussal crab were given name changes in honor of their duties performed during the crisis. Jala was changed to Jaller, Maku was changed to Macku, Puku was changed to Pewku, Hali was changed to Hahli, and Huki was changed to Hewkii.

Maori Lawsuit
The holiday was an in-universe way of expressing the mandatory name changes of certain BIONICLE characters, due to the Maori Lawsuit. The Maori Lawsuit was casted by the Maori people who were angered at LEGO's lack of respect for their words. They soon decided to take legal action against them, and won. As a result many of the names of characters had to be changed, and LEGO decided to come up the with the Naming Day Celebration to explain the sudden name changes of certain characters, like Jala (Jaller), Maku (Macku), Huki (Hewkii), and Puku (Pewku). Lego also changed Tohunga to Matoran and at the time the story reason was that the Matoran had finally realized that they were one people, although the idea was later dropped and never remained canon.

Trivia

 * In "Fractures", the Coliseum is stated as the "home of Naming Day ceremonies", so it is believed some of these happened on Metru Nui.