It is shorter than the katana , which was well known in the beginning of the 17th century as a kodachi sword . The two swords were always carried together : the wakizashi finished off the work of the katana sword . Later , the term was used to denote the group of swords which were shorter than the main sword of the samurai , and as a result , wakizashi acquired the meaning of the side sword , because a side sword was shorter than the main sword by its nature .