Dom Pedro is the Portuguese form of the name of Pedro I, the first emperor of Brazil, best known for proclaiming the country's independence in 1822. The phrase 'sai, derrotado' simply means 'leaves, defeated' in Portuguese, so the clip plays like a mock historical bulletin announcing his downfall. Circulating as a short meme audio in Brazilian internet culture, it gets reused whenever creators want a grandiose way to declare someone beaten. The joke works because it treats an ordinary fail with the ceremony of a history book chapter ending.