fiduciary
adjective
[ fɪˈdjuːʃ(ə)ri ]
• involving trust, especially with regard to the relationship between a trustee and a beneficiary.
• "the company has a fiduciary duty to shareholders"
• (of a paper currency) depending for its value on securities (as opposed to gold) or the reputation of the issuer.
fiduciary
noun
• a trustee.
Origin:
late 16th century (in the sense ‘something inspiring trust; credentials’): from Latin fiduciarius, from fiducia ‘trust’, from fidere ‘to trust’.