Getting Created By 'name' of sys_created_by on sysapproval_approver table

For System Notifications, on the sysapproval_approver table.

The field, "Created By"   (sys_created_by), is a string field, not a reference.

The Created By displays the "user_id" of the user, instead of their "name".

How can I get the name?

In the body of the email I have:

Created By:   ${sys_created_by.name}     =     of course since this isn't a reference field, it returns nothing.

Created By:   ${sys_created_by}     =     this returns the user_id, like   489593

Can I use the good 'ole getReference() function in an email notification?