As I understand it ; *ISIS* is a general term made up by the media derived from the United Nations coining all militants *ISIN* (no big surprise there). Apparently the UN and the US govt wanted to generalize Islamic militants no matter what factions (and there are many), into a general name such as ISIN- Islamic state of IraQ nation).
So ISIN is the official UN name for ANY militant in that region. *ISIS was coined by the media - Islamic state of IraQ and Syria, which the media likes better so it stuck, and it sounds so much better as another boogie man - with a twist - you can't really define who or what faction, or which group did what or even if they really matter or not, but the effect of the name = perfect.
Wondering though..if any Saudi heads have been rolling lately?... The Saudis apparently have been air striking militants without US approval (God forbid!)