why did tor use .onion?

[Ivan]

they could have used .tor .private or anything else.
so my question is why did they choose onion

[Cantra]

The tor network uses an 'onion routing' security technique, where a text file is wrapped in multiple layers of encryption, which are removed one by one, peeled off like the layers of an onion.
Since that's the security the Tor network is based on, they use .onion as a (pseudo) top level domain identifier.