E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Amicus curiæ (Latin, a friend to the court).
One in the court who informs the judge of some error he has detected, or makes some suggestion to assist the court.
Amicus Plato, sed magis amica Veritas (Plato I love, but I love Truth more) A noble dictum attributed to Aristotle, but certainly a very free translation of a phrase in the Nicomachean Ethics (Where both are friends, it is right to prefer Truth)