I feel like this is trying to simplify something that can’t be simplified so easily, and perhaps shouldn’t be. The desire to reduce such a complex and broad problem space suggests to me a lack of understanding of what a simplification entails. Using these different words may only present confusion in other directions.

Login isn’t always what authentication is about. In fact, I recently wrote an authentication layer for identifying users based on something that would have been sent to their email, but they don’t exist as users in the system yet. They can’t log in. They don’t even need to in order to utilize this authentication layer. So it isn’t login, yet it’s a form of authentication.

Permissions is a good word I guess, but it’s as specific as authorization. Why change it?

Maybe I like auth because it’s familiar. I am open to new ideas though. This one just doesn’t seem to make sense.