I've previously written about how the word fanatic originally referred to someone with religious fervor, and the same is actually true for the word zealot. That term originally referred to a religious sect in the Roman province of Judaea, who were so passionate about their cause that they killed themselves en masse before the Romans took over their fort during the Siege of Masada. Since then, zealot has become more figurative and can be applied to anyone who is uncompromising in their beliefs (also specifically as an epithet for the apostle Simon). Through Latin, the word derives from Ancient Greek zelotes, meaning "zealous follower". That's from the word zelos, which meant and is the etymon of "zeal". Finally, zelos comes from Proto-Indo-European ya, meaning "desire".
Hello! I'm Adam Aleksic. This year, I graduated from Harvard University with a degree in Government and Linguistics. There, I co-founded the Harvard Undergraduate Linguistics Society and wrote a thesis on Serbo-Croatian language policy, magna cum laude. In addition to etymology, I also really enjoy philosophy, trivia, vexillology, geography, board games, conlanging, art history, and law.