Remember reading something along those lines, definitely originates from Hashish

This is not Afgani. The term arises from a cult founded in Syria in the period of the First Crusade. The cult grew to a number of chapters throughout the Middle East. Assasin's were largely used in the power struggles of the Arab factions, however, several famous incidents were recorded dealing with the Crusader aristocracy. Perhaps, the most famous is the assasin story associated with Richard the First of England. The use of drugs to emulate paradise is as you suspect. Best, wjr

I've read that they were originally called "Hashashin" (that could be spelled incorrectly), owing to their use of hashish before missions. -HoH

The myth that the Hashshashin used Hashish is just that, a myth. The similarities in name is only a coincidence. At least thats what I've been led to believe in my reading about assassination.

If it is a myth, it is one that is oft repeated in a huge number of sources. Of course, consideration of word origins are often subject to angels dancing on the head of a pin sort of debates.

There are a few theories on where the word Assassins came from here is one in connection with the Nizari Isma'ilis (later known as "The Assassins"). By the way they were a Shia sect.

Forgot the Quote. 'Assasseen' in Arabic signifies 'guardians', and some commentators have considered this to be the true origin of the word: 'guardians of the secrets'." - Arkon Daraul, Secret Societies

The Hashishins were extremely competent at killing high profile figures during the middle ages. Their assasination cell network spanned from north Africa to Afghanistan. At it's height the cult was responsible for the assasination of 2 Caliphs of the Ommayid Dynasty, one Turkish, some half dozen Frankish leaders of the European 2nd crusade, and the right hand general of the Mongol warlord Tamerlane, within the span of 5 years.

Another interesting word that seems to have originated with the Assassins was "Fedayeen", the Arabic root "fidâ'î, meaning "one who is ready to sacrifice his life for the cause".

I believe that the Haschishins was a sort of muslim cult, based on the illumination with the use of drugs (haschish) and the sacralization of murder (>>> assassination)