The word assassin, I assumed, would not be Indo-European, based off its unusual formation. This conclusion was correct; it is from Arabic, by the normal route through Italian then French (in this case by assassino and the homonym assassin, respectively). But what is curious here is the semantic change: in Arabic, the word was pronounced something like hashshashin and literally meant “hashish addicts”, hashish, of course, being a form of marijuana. The connection exists in an 11th century Ismaili cult led by a man named Hasan Ben Sabah, a group which would send out its highly trained initiates to kill opponents- only after rituals where they had to intoxicate themselves with cannabis. Hashshashin, of course, is connected to the word hash (slang for “weed”, not to be confused its homophones, which have different etymologies), a shortening of hashish (still in use, though even less common now). All of this comes from Arabic hasis, or “dried herb”, from a Proto-Semitic source. In the transition from hashshashin to assassin, you may have noticed all the h’s were dropped. It is relatively common for an sh to become just an s, and a word starting with h and a vowel to lose the h; see my post on humble pie about the opposite effect. But, anyway, I’ll never look at a murder mystery show the same way again.
Adam Aleksic has been described as the internet's sixth most famous etymologist. He loves writing about himself in the third person, he's a freshman at Harvard University, and he has disturbing interests in linguistics, vexillology, geography, board games, limericks, and law.
The Etymology Nerd