Thanks @cascat07 , I checked it up and it really means “sword”, according to Google Translate.
@Bruno_Frank_Hill, Samurai used primarily bows and spears in their battles. The Katanas were more commonly used for self-defense and ceremonial purposes. It was kinda like their side-arm. It only became really popular in more modern times.
Also, at least in Europe, warriors used weapons from downed enemies and allies extensively. You’d be lucky to get in and out of a battle with the same weapon in hands. Or with limbs, for that matter.
Ninjas were more like spies than warriors. Not spy like James Bond, but spy like the NSA. They just dressed up as peasants and stuck around the enemy, hoping to learn something useful. Even their efficacy in assassinations is debatable. Their weaponry was mostly meant for self-defense if they screwed up and the enemy recognized them, thus, they were very short to be easily concealable, and more often than not mocked up to pass off as tools. Some were tools.
@Sneaks, I was told that they didn’t use shields because they saw it as dishonorable, and because the steel available at the time was really crappy, so basically any armor was capable of breaking the enemy’s weapons, and a shield was just a encumbrance for that reason. The Europeans also moved away from shields once they got better at making armor. Also, Katanas (and swords in general, to be honest) are known for breaking during parry maneuvers.
Also, the fact that Samurai started as mounted archers, and oriental swordsmanship is heavily oriented on using both hands to attack, heavily influenced their decision not to use it. The samurai had three main weapons; the bow, the spear, and the Katana. Katanas are dual handed, spears are dual handed, and bows are dual handed. Implementing a shield in their load-out would mean having to re-learn everything from scratch. Samurai warfare was relatively rare, anyway.