1. a person to whom property or power is entrusted for the benefit of another.
2. of or pertaining to the relation between a fiduciary and his or her principal: a fiduciary capacity; a fiduciary duty.
For the vast majority of those here, our responsibility ends in the mirror. Maybe you are managing money for others and that term applies, I don't know.
People maintain anonymity for a reason and it is rarely noble.