Mentioned three times, but never defined. From Brewer:
Silhouette (3 syl.). A black profile, so called from Etienne de Silhouette, Contrôleur des Finances, 1757,
who made great savings in the public expenditure of France. Some say the black portraits were called
Silhouettes in ridicule; others assert that Silhouette devised this way of taking likenesses to save expense.