Who coined the word "assassination"?

Answer 1

William Shakespeare if I am right

Answer 2

The term 'Assassin' is thought to be derived from its connections to the Hashshashin, a militant religious sect of Ismaili Muslims, thought to be active in the Middle East in the 8th to 14th centuries. This mystic secret society killed members of the Abbasid elite for political or religious reasons.

It was said that they were drugged during their murders, often with materials such as hashish and opium. The name assassin is derived from either hasishin for the supposed influence of the drugs, and disregard for their own lives in the process, or hassansin for their leader, Hassan-i-Sabah.

Today, it is known that hashishinnya was an offensive term used to depict this cult by its Muslim and Mongolian detractors; the extreme zeal and cold preparation to murder makes it unlikely they ever used drugs. As far as is known they only used daggers, rarely survived their attacks, even when successful (unlike in many tales, where they are silent, invisible killers) and it seems that they rarely acted against westerners during the Crusades, partly because the crusading orders were not as affected by losing individual leaders as were the autocratic local regimes of the time

Answer 3

Not sure who first coined the word, but I know something of its roots. The Hassassin were a tribe (Arabs, I think) who would eliminate their competition, often in the middle of the night, and working in secret. Therefore those that were killed by stealth were "assassinated".
Hope that helps.

Answer 4

The term 'Assassin' is thought to be derived from its connections to the Hashshashin, a militant religious sect of Ismaili Muslims, thought to be active in the Middle East in the 8th to 14th centuries.