It’s historically been abbreviated AAA “triple A” for Access, Authentication, and Authorization. Each being a separate system, VPN’s and Firewalls traditionally controlling access for example.
I've also seen AAA used, but standing for Authentication, Authorization, and Accounting. The Wikipedia page [1] is short, but it refers to the context I've seen that in.
[1] https://en.wikipedia.org/wiki/AAA_(computer_security)