Fiduciary
Etymology
From Latin fiduciarius, "held in trust," from fiducia, "trust, confidence," in turn from fidere, "to trust" (related to fides, "faith"). The literal notion is a relationship resting on trust. Law made it a demanding legal status: the fiduciary owes duties of loyalty and good faith, the strictest obligations one person can owe another.
noun · /fih-DOO-shee-air-ee/
A person legally obligated to act in another person’s best interest rather than their own.
What it names
The higher standard your trustee, financial adviser, or company director is held to — they must put your interests ahead of any personal gain.
Example
As a fiduciary, the pension manager could not steer clients into funds that quietly paid him kickbacks.
Related idea
A fiduciary owes an active duty of loyalty; someone acting merely bona fide is only required to be honest, a far lower standard.