Three Nanba prison guards who serve under Head Warden Momoko Hyakushiki - Kiji Mitsuba, Kenshirou Yozakura and Samon Gokuu - are named from a Japanese folktale about Momotaro, a folk hero born from a peach ("Momo" in the Head Warden's name), who befriended a pheasant, a dog and a monkey (respectively "kiji", "ken" and "samon" in their names). Each has decorations on their uniform referencing a bird, a dog, and a monkey.
The show is set in Nanba Prison. "Nanba" means "Number". Most of the characters (especially the prisoners) are named after numbers.
The series title "Nanbaka" is a portmanteau of the Japanese words "nanba" (after Nanba Prison) and "baka" (fool).
Head Warden Momoko Hyakushiki is named after the number 100 (which is written in Japanese as both "momo" and "hyaku").
The Daisen brothers Rokuriki, Kokoriki and Youriki are named after "roku", "koko" and "you" (the Japanese words for 6, 9 and 8) and "riki" (the Japanese word for "power").