E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Hats and Caps.
Two political factions of Sweden in the eighteenth century, the former favourable to France, and the latter to Russia. Carlyle says the latter were called caps, meaning night-caps, because they were averse to action and war; but the fact is that the French partisans wore a French chapeau as their badge, and the Russian partisans wore a Russian cap.