The History of this belt comes from the Tracy's Kenpo Karate Home Page
This page contains a brief history of the Kenpo karate Kyu ranking.
Nikyu is the second rank below black belt in Kenpo Karate, karate and all martial arts that use the Japanese Kyu/Dan ranking. See Ikkyu for an explanation of Kyu ranking. The Japanese for 1, 2, 3, is ichi, ni, san, and therefore, Ikkyu (1-Kyu) Nikyu (2-Kyu) Sankyu (3-Kyu), and this tradition is followed in Kenpo Karate, while Kempo, American Kenpo and Chinese Kenpo usually do not use Japanese terms.
Below Nikyu is Sankyu (3rd Degree Brown Belt). Kenpo Karate also uses the English words to avoid confusion but the Kenpo Karate belt rank for 2nd degree brown belt is always awarded as Nikyu, usually with the English equivalent next to it, or under it. Nikyu is a rank of skill and honor that can only be awarded by Kenpo Karate Yudansha (one who holds a Dan rank) who has received a Dan ranking from higher ranked Yudansha. The skill and requirements for Nikyu in Original Kenpo Karate are, therefore, higher than 2nd degree brown belt in American Kenpo, and represent the time honored tradition of the Japanese belt ranking that was the original ranking of Kenpo Karate in Hawaii.