From the handy, dandy etymology dictionary:
assassin - 1531 (in Anglo-L. from c.1237), via Fr. and It., from Ar.
hashishiyyin "hashish-users," pl. of
hashishiyy, from
hashish (q.v.). A fanatical Ismaili Muslim sect of the time of the Crusades, under leadership of the "Old Man of the Mountains" (translates Ar.
shaik-al-jibal, name applied to Hasan ibu-al-Sabbah), with a reputation for murdering opposing leaders after intoxicating themselves by eating hashish. The pl. suffix
-in was mistaken in Europe for part of the word (cf.
Bedouin).
Not to disagree of course. I just wanted to point out the it's a lot older than the days of Reefer Madness. (And it's taken great effort on my part not to commence a diatribe on my own views of the evils of drug use.