On April 1, 1572 Dutch rebels captured the town of Den Briel from Spanish troops led by Lord Alva. This military success eventually led to the independence of the Netherlands from Spain. A Dutch rhyme goes: "Op 1 april / Verloor Alva zijn Bril." This translates to: "On April 1st / Alva lost his 'glasses'". "Bril" means glasses in Dutch, but is also a pun on the name of the town, Den Briel.
According to Dutch legend, the tradition of playing pranks on April 1st arose to commemorate the victory in Den Briel and humiliation of the Spanish commander.
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