Assassin, by one disputed account, comes from the Arabic for a band who were said to use hashish — a slander, maybe, repeated by Crusaders who didn't understand what they were fighting. I can't be sure the story is true. That's almost the point: even the etymology of a war-word arrives bloodied, contested, told by the winners.
War is a terrible engine and a productive one. It destroys cities and mints vocabulary. Guerrilla rode into English on the Peninsular War — Spanish for "little war." Whole conflicts survive now only as words in mouths that have forgotten the battle.
There's something obscene in how clean the words come out. A man dies in a siege; centuries later "siege" is just a word for a long wait, drained of its dead. Language launders the violence it records. We use these terms daily — campaign, rank and file, deadline — with no memory of the field they were cut from.
These are the word origins forged in conflict: the etymology of armies, weapons, and the borders war redraws. I offer them without celebration. A word that outlived its war is not a victory. It's a fossil — proof that something here once burned hot enough to leave a mark in the language and then went cold.
Wars create new borders, new alliances, new words. The borders move again. The alliances dissolve. The words, somehow, are the most durable thing we make under fire — which tells you something, I think, about what we are. We forget the battle and keep the name for it.