Agent Bank

It's the place you store your agents safely, in their purple suits and weird haircuts, producing about 2% of an agent each year.

And also, if you get someone to do something for you, for a fee or some form of payment, that person becomes your agent. If you get a bank to do something for you, that bank becomes your agent bank. (And presumably, if you get a horse to do something for you, that horse is your agent horse...and so on.)

The details of what an agent bank might do for you changes from situation to situation. Typically, it has to do with running various paperwork, or providing back-office functions, like conducting credit checks.