"Katipunan" stands for "Kapatiran ng mga Estudyanteng Nag-aaral ng Pilipino sa Unibersidad ng Hawai'i. This roughly translates into meaning the "Confraternity of students taking Filipino courses at the University of Hawai'i System."
The name was inspired by the secret society founded by heralded Philippine hero, Andres Bonifacio, during the Filipino-Spanish War in 1896. This society specifically used Filipino as a form of secret correspondence and utilized traditional rituals in order to promote their unity and identity. Read more about the Katipunan at Wikipedia and at the UH Office of Multicultural Student Service's "The Philippine History Site".