Our word asylum comes from the Latin word asylum, with basically the same definition. This is from Greek asylos, which meant "sanctuary" literally. The "mental health institution" meaning, attested in 1773, came from the "safe space" meaning (attested in the 1640s), as in how asylums ensure the safety of mentally ill patients. Here we can eliminate the prefix a-, which meant "without" (allegedly from the Proto-Indo-European root ne, meaning "not"). What's left is another Ancient Greek word, syle, which, curiously enough, was actually a legal term, referring to the city-states' rights of seizure. Syle does not have a confirmed word origin, but it also likely comes from Proto-Indo-European. So, technically, asylum means "without the right of seizure", which results in a pretty democratic madhouse. Usage of asylum peaked in the twentieth century, but it's recently experienced a bit of a rebound, accounting for about 0.00057% of all spoken words
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd