The word assassination is derived from Nizārī Ismāʿīliyyah, a religio-political movement that arose in the late 11th century within the Ismāʿīliyyah branch of Shiʿi Islam. The Nizārīs, whose power base was in the Elburz Mountains, in what is today northern Iran, lacked the military strength to confront regional opponents such as the ʿAbbasid caliphate and the Seljuq sultanate directly. Instead, they relied on subterfuge and infiltration to strike at key military and political figures within both empires.
European Crusaders heard and misinterpreted legends about the early Nizārīs and then brought these stories back to their home countries. Two of these misinterpretations—which likely originated with the Nizārīs’ enemies—were that the Nizārīs were fanatics under the sway of the mysterious “old man of the mountain” and that they used hashish to induce visions of paradise before setting out to face martyrdom. The Arabic term ḥashīshī (“consumer of hashish”), which was used as a derogatory term for the Nizārīs, became the root of the English term assassin and its cognates in other European languages. Assassin took on the meaning of a relentless killer.