As a secondary weapon to a Katana, they are known together as a "Daishō" (大小), literally meaning "Big-Small", with "Big" referring to a Katana, as the main blade, and "Small" referring either to a Wakizashi or a Tantō (短刀), as the companion blade.
The wakizashi has a blade between 30 and 60 cm, (12 and 24 in), with wakizashi close to the length of a katana blade being called "o-wakizashi", and wakizashi closer to the length of a tantō blade being called ko-wakizashi. The wakizashi being worn together with the katana was the official sign that the wearer was a samurai or swordsman of feudal Japan. When worn together the pair of swords were called daishō, which translates literally as "big-little". The katana was the big, long or main sword, and the wakizashi the companion sword. Wakizashi are not necessarily just a smaller version of the katana; they could be forged differently and have a different cross section.
The Wakizashi have been in use as far back as the 15th or 16th century. The wakizashi was used as a backup or auxiliary sword; it was also used for close quarters fighting, to behead a defeated opponent and sometimes to commit ritual suicide. The wakizashi was one of several short swords available for use by samurai including the yoroi tōshi, the chisa-katana and the tantō. The term wakizashi did not originally specify swords of any official blade length and was an abbreviation of "wakizashi no katana" ("sword thrust at one's side"); the term was applied to companion swords of all sizes. It was not until the Edo period in 1638 when the rulers of Japan tried to regulate the types of swords and the social groups which were allowed to wear them that the lengths of katana and wakizashi were officially set.