A band of Carmathians, collected by Hassan, subah of Nishapour, called the Old Man of the Mountains, because he made Mount Lebanon his stronghold. This band was the terror of the world for two centuries, when it was put down by Sultan Bibaris. The assassins indulged in haschisch (bang), an intoxicating drink, and from this liquor received their name. (A.D. 1090.)
“The Assassins ... before they attacked the enemy, Would intoxicate themselves with a powder made of hemp-leaves ... called hashish.” —J. Wolff.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894