Sephiroth (or Sefirot) is a name that comes from Kabbalah, a Jewish system of beliefs. This system was a way to understand the nature of God and how people relate to Him. The relationship is explored through magical symbols (the most important one being the tree of life)
The tree of Life consists of ten spheres, called Sephiroth (sing: Sephirah) interconnected by twenty-two paths. The symbol itself along with the Sephiroth are open to interpretation.
The Masamune was a supposed sword that had a great deal of sharpness and strength. This Katana blade really kicked.
HISTORY:
Sephiroth, as you people know is one bad guy, but you already know that... well don't you? He used to be the top officer in the Shin-Ra corporation. Well one day he found out that he was an experiment to bring back the race of the Ancients or Cetra, and went crazy. He thought he was an Ancient. But all he had in him were a few Jenova Cells. Sephiroth's father is a scientist that also worked for Shin-Ra and well he got it on with a woman named Lucrecia... and one thing led to another and she got pregnent. When Sephiroth was in her woumb, he got injected with the Jenova Cells. So when little Sephiroth was born he was already a little ass-kicker.