Kabuto is a type of helmet first used by ancient Japanese warriors, and in later periods, they became an important part of the traditional Japanese armour worn by the samurai class and their retainers in feudal Japan.
Japanese helmets dating from the fifth century (long before the rise of the samurai class) have been found in excavated tombs. Called mabizashi-tsuke kabuto (visor-attached helmet), the style of these ancient helmets came from China and Korea and they had a pronounced central ridge. The kabuto was an important part of the equipment of the samurai, and played a symbolic role as well, which may explain the Japanese expressions, sayings and codes related to them. One example is Katte kabuto no o o shimeyo (lit. "Tighten the string of the kabuto after winning the war"). This means don't lower your efforts after succeeding (compare to "not to rest on one's laurels"). Also, kabuto o nugu (lit. "to take off the kabuto") means to surrender.