When I first read about them years ago, I was intrigued about  their supposed use of hashish being part of the etymology of their Arabic name, although it would appear that it was more of a slur by their enemies than an actual fact.   

"The name "Assassin" is often said to derive from the Arabic word Hashishin or "users of hashish",(which can be used as a derogatory term in Arabic and it is the equivalent of "drug addict", in this case, "hashish addict")"