The word assassin comes from an old order of warriors who did a lot more than assassinate their enemies -although they did plenty of that, too.
In the year 1090, a charismatic man by the name of Hasan-i Sabbah used his popularity to gather together a small but devout following of Ismaili Muslims. Sabbah single-handedly molded his following – known as the Order of the Assassins, or Hashashin – into a fighting force capable of bringing down the most well-guarded leaders of the day. Zealous and disciplined, this force would strike terror into the hearts of caliphs, viziers and sultans for the next 200 years.
Sabbah’s Order of the Assassins fought for power against Christians and rival branches of Muslims. The Order was outnumbered and scorned by the Sunni majority. But despite this, as Jefferson M. Gray of Historynet.com says, “Hasan-i Sabbah and his successors were brilliant practitioners of asymmetric warfare. They developed a means of attack that negated most of their enemies’ advantages while requiring the Assassins to hazard only a small number of their own fighters.”
Not only does the name live on, so do their tactics, emulated by armies, spies, organized crime, and terrorists. Read about those tactics -they'll probably seem familiar in today's world- at Environmental Graffiti. Link