Wakizashi

The wakizashi was "The side arm" given to bushi children at an early age. Once received the wakizashi never left the samurai's side, unlike the katana. It is similar to the katana, but shorter in length. The wakizashi was usually worn together with the katana by the samurai. The combination of the wakizashi and katana was called daishō, meaning "large and small";The katana being the sword and the wakizashi the companion sword.

Etymology
Originally, the term "wakizashi" refered to any sword worn with the katana. By the samurai, the wakizashi meant any sword shorter than their main sword, the katana. As a result any side sword became the "wakizashi", such as the tantō (dagger).