The daishō (大小, literally "big-small)" is a Japanese term for the traditional pair of swords carried by samurai in the feudal era.
The two weapons making up the daishō are the katana (刀) and the wakizashi (脇差), the former being the longer one, it corresponds to the attack weapon, while the other is more like a parrying weapon.
Thus this explains the very etymology of the word, which comes from the terms daitō (大刀, large sword) and shōtō (小刀, small sword): daitō associated with shōtō gives daishō.
However, daishō originally referred to the carrying of any long and short uchigatana together, not specifically that of a katana and wakizashi.
Sometimes a pair of tantō is also considered a daishō, and finally the term daishō sometimes simply refers to a paraphernalia of two roughly identical swords.
During the samurai period, the blades of the daishō could be similar because they were made by the same craftsman, but this practice was relatively rare because it was more expensive, and furthermore the matching of the two swords was not of great importance at the time.
The concept of the daishō originated during the Muromachi period (1336-1573), during which it was common to cross match a short sword with one of any length. At one time, the tachi and tantō would have been wielded together, as would later two uchigatana of different sizes.
With the advent of the katana, the wakizashi was eventually chosen by the samurai to replace the tantō. In his book The Japanese Sword, Kanzan Satō notes that there did not seem to be any particular need for the wakazaishi, and suggests that the wakazaishi probably became more popular than the tantō because it was more suitable for indoor fighting.
According to most traditional schools of kenjutsu, which are part of the koryū, only one of the two blades of the daishō was used for fighting.
However, during the first half of the seventeenth century, the famous fencer Miyamoto Musashi promoted the use of the one-handed grip that allowed two swords to be wielded simultaneously.
This technique, called nitōjutsu, is one of the basic elements of the Hyoho Niten Ichi Ryu style, a school teaching the art of swordplay founded by Musashi.
Following the "sword hunt" ordered by Toyotomi Hideyoshi in 1588, the daishō was reserved exclusively for the samurai class and thus became a symbol of their rank.
The daishō probably became popular during the last years of the Muromachi period since the first examples of its use date from the end of the 16th century. Subsequently in 1629, an edict defining the rights of samurai was instituted and required the wearing of the daishō.
During the Meiji era a second edict written in 1871 annulled the first one, and in 1876 the wearing of the sword in public was banned for most of the Japanese population, which made it definitively the symbol of the samurai.
The end of the Edo period saw the banning of swords and consequently the disappearance of the samurai class.
When the katana is on its display, it is placed :
Most often, only the "mount" of the sword is exposed like this (tsuka, tsuba and saya, held together by a wooden blade).
In fact the blade is often stored in a hermetically sealed white wooden protective mount called shirasaya (which are not intended for combat).
In times of peace, the katana is placed on the display, the tsuka on the left side, while in times of war, the tsuka is on the right side, this to allow a faster exit of the katana in case of danger.