A person who creates or administers a fideicommissum; someone who establishes a trust or manages it on behalf of another.
From 'fideicommission' plus '-er' (agent suffix). The '-er' transforms the noun into an agent noun meaning 'one who does the action.'
A fideicommissioner in Roman times had serious power—they controlled wealth that technically belonged to someone else, making them one of history's earliest professional wealth managers.
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