The word mystery was first used in a 1350 poem by William of Shoreham, with the spelling mysterye. Other forms around that time included misteri, misteria, mystere, mystri, misterye, and dozens more; our modern spelling didn't get standardized until the seventeenth century. The noun comes from Anglo-Norman misterie and Old French mistere, which had pretty much the same definition but were used more often in the context of religious concepts that humans couldn't understand. Those come from Latin mysterium and Ancient Greek mysterion, which referrred to secret rites and sacraments, and the root there is mystes, meaning "initiated one". Going further back, mystes is from the verb myein, meaning "to close", possibly in reference to the eyes or lips of those initiated into secret religious organizations. Indeed, we've seen both meanings develop from it: myein also gave us mute, which involves a closed mouth, and myopia, which was associated with closed eyes.
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.