Merriam-Webster Collegiate Dictionary - assassin

 noun  Etymology: Medieval Latin ~us, from Arabic ?ashshashin, plural of ?ashshash worthless person, literally, hashish user, from hashish hashish  Date: circa 1520  1. capitalized a member of a Shia Muslim sect who at the time of the Crusades was sent out on a suicidal mission to murder prominent enemies  2. a person who commits murder; especially one who murders a politically important person either for hire or from fanatical motives