For me the difference between "gate keeper" and "protector" is that the gate keeper decides who gets to know me how well. It is a rather proactive job. My protector parts react to an event/trigger...
Most of my parts were created to protect the core and could, as such, be called protectors. Although I have functional parts created to excel in a specific area. Because we don't use names we have to come up with other discriptive ways to know who is who.
That and we are all obsessed with language and how it is used.