Kikkō (Japanese: 亀甲, translated as "Turtle Shell") refers to plates made of iron or hard leather that were used as part of the armors of Samurai and Ashigaru in feudal Japan, similar to scale armor.
Structure of Kikkō
Kikkō are small, hexagonal plates, which are designed to resemble the shape of turtle shell plates and are therefore named accordingly.
Individual Kikkō were sewn onto the fabric lining of the armor using holes drilled into the edge or center, or alternatively, the plates were interconnected like chainmail through these holes.
This either formed the outer layer of the armor or the Kikkō were concealed between two layers of fabric, serving as hidden protection against attacks. The resulting Kikkō armor was used in every class of Samurai and foot soldiers.
In the West, this type of armor was described among others by George Cameron Stone. In his 1934 work, Stone referred to "scale armors" made of "small hexagons" that were frequently used in Japan, made of "steel or hard leather" and "occasionally enveloping the entire body".
Usage of Kikkō
Traditional Japanese armors, including Sune-Ate (shin guards) and Tate-Eri (shoulder plates) were often reinforced with Kikkō. The Haidate (skirt for thigh protection) and Kote (armor for arms and hands) were partially or completely covered with these plates.
Light, foldable armors (kikkō tatami gusoku) could be built from Kikkō, which even featured a foldable breastplate (kikkō tatami dō). Other types of armor, such as Waki-Biki and Manjiyuwa, could also be equipped with Kikkō. The helmets of the Samurai (Kabuto) often had a neck protector (shikoro) made of Kikkō sewn onto a fabric base.
In the book "Arms and Armor of the Samurai: The History of Weaponry in Ancient Japan" by Ian Bottomley, published in 1994, a forehead protector (hitai are) with a hood made of Kikkō is described. There is also mention of the kikkōganedō, the foldable breastplate made of the said plates.