means A short man with an outsized hunger for power or grandeur — or, depending on context, a layered puff-pastry dessert with cream filling, a card game, or a former French gold coin.

from All senses trace back to Napoleon Bonaparte (1769–1821), the Corsican-born French emperor whose name became shorthand for ambition in a small package. The 'short man' stereotype gave us the figurative sense, and 'Napoleon complex' later named the supposed overcompensation of small men. The pastry, oddly, may not honor the man at all: the popular tale links it to him, but it's more likely a reshaping of 'napolitain,' meaning 'of Naples,' the French having borrowed an Italian layered-pastry idea — so the dessert's emperor may be a delicious coincidence.