The name Sephiroth was a name cleverly picked by Squaresoft, because if you look up information on the word "Sephiroth" you will see that it comes from the teachings of the Kabbalah, which is a very interesting subject. In the Kabbalah's teachings there are 10 Sephiroth (plural: Sephirah) symbolised in the Tree of Life. Each Sephiroth represents a path of ideas, attributes and concepts that one must realise and understand within oneself. Once that is done a person will have reached divine perfection, realised their Inner Christ and so forth. I find this extremely interesting in relation to Sephiroth-sama, as throughout the game he is striving to become like a god, to reach that perfection, and to go to the Promised Land. I hope I have given you an [accurate] insight into the meaning behind Sephiroth's name. I am no expert on the Kabbalistic teachings, what I have written is only a [very] brief summary of what I have understood from reading through various webpages. If this has interested you I strongly suggest looking up this subject further, so you can understand for yourself the significance of Sephiroth's name