How We Went from Hashish to Assassin
Bickering about God
First the Sunnis and Shiites split off from each other to squabble about who was right. Soon even the Shiites couldn’t agree amongst themselves, and the Ismaelites split off from the main group only to continue to squabble some more in the reduced faction. Everyone was a heretic according to somebody else, but the Sunnis and the Shiites could agree on one thing at least: the Ismaelites were definitely the most heretical of all. The Ismaelites were also the smallest group, so in order to hold their own against the big guys, they had to come up with sneakier tactics.

Toward the end of the 11th century, an Ismaeli named Hasan-i Sabbah put his sneaky brain into establishing one of the sneakiest and most successful orders ever to sneak about the Middle East. Hasan found himself a nice impenetrable castle on a cliff face in the middle of nowhere, and from there he commanded a deadly group of killers who quickly had the rest of the Muslim world shaking in their boots.
In contrast to the huge armies available to the Sunnis and Shiites, Hasan’s tactics involved sending a lone killer to strategically dispatch leaders of the other sects. This one man was completely devoted to the single task of knocking off his target, often taking months or even years to slowly infiltrate his way into the enemy’s trust before carrying out the deed. This was terrifying because the enemy leaders could never be sure they could trust their closest friends.
Hasan’s killers almost always knocked off their target in a massively public place, thereby sending a strong message to a giant crowd of screaming witnesses. This tactic was very effective, and it was also completely insane and suicidal, as the murderer himself would inevitably be tackled and killed right then and there.

Whether or not it was true, it soon became a common belief that the only way these killers could possibly have the nerve and the idiocy to carry out such jobs was that they must all be addicted to hashish. They became known as the Hashshashin, which you might notice sounds like the word assassin if the speaker is somewhat slurring his speech.
When the legend of this deadly faction eventually spread back to Europe, the pronunciation got changed in translation a little and the word came to be associated with any hired political killer. Etymologically speaking, however, assassins still are, and always will be, denoted “hashish eaters.”