1800-1900Frenchéminence grise ‘gray eminence’, originally used of Père Joseph, adviser of the French minister Cardinal Richelieu
Examples
EXAMPLES FROM THE CORPUS
The networks set up by De Gaulle's eminence grise, Jacques Foccart, were replaced or strengthened.
someone who has unofficial power, often secretly, through someone else: Borusa had no wish to become president, instead preferring to operate as an eminence grise behind the scenes.