“Le petit caporal. Fr. — "The little corporal." A familiar name given to NAPOLEON by the French soldiers after the battle of Lodi.” From:
A new dictionary of quotations from the Greek, Latin, and modern languages: translated into English, and occasionally accompanied with illustrations, historical poetical, and anecdotal, with an extensive index, referring to every important word. 8th edition. Published by J.B. Lippincott & Co., 1869. 527 pages:
“On ne passe pas, quand bien meme qu'encore tu serais le petit caporal. (You cannot pass not even if you were the "little corporal" himself.) Attributed to Jean Coluche, the sentry of Ebersberg, to Napoleon, but he really only said On ne passe pas! (You cannot pass!) Cf. L'Illusttation of 1846 and the Journal du Loiret, August 29, 1862. According to the Memotial de Sainte-HeIene (vol i., p. 232), the sobriquet "le petit coporal" originated from the singular custom of the oldest soldiers giving after each battle (during the Italian campaign) a new title to their young general. He was made corporal at Lody and sergeant at Castiglione. The soldiers continued to call him " le petit caporal."
See p. 159, Famous sayings and their authors, 2nd edition (1906), by Edward Latham: