The first use of "katana" as a word to describe a long sword that was different than a tachi is found in the 12th century. These references to "uchigatana" and "tsubagatana" seem to indicate a different style of sword, possibly a less costly sword for lower ranking warriors. The evolution of the tachi into the katana seems to have started during the early Muromachi period (1337 to 1573)