Kama refers to a farming tool. Much like the sickle, it's made for cutting crops and farming rice. It was used as an improvised and easily hidden weapon. Being seen as a farming tool, it could even be hidden in plain sight. Due to this nature it was a preferred weapon for the ninja. It is still used in martial arts training. A famous trick was to attach rope or chain to it so that it could be thrown and be used to trap enemies.