I know someone whose major in college was abbreviated as Isys (information systems). Not anymore.
The credential management system at my college was called ISIS, so you had an ISIS identifier, you had to go through ISIS login, etc.
Re:“Username cannot contain 'clyde'”
by peepee1982 on Monday November 21, 2022 @03:50AM
(#33690344)
And let us not forget The International Secret Intelligence Service in Archer.
[1] https://en.wikipedia.org/wiki/Softcard