Flamengo, based in Rio de Janeiro, is one of Brazil's most supported and most rivalled football clubs, so chants against them travel fast among opposing fans. Ta morto is informal Portuguese for is dead, used here not literally but as football slang for a team that looks finished in a match or season. The phrase became a shareable taunt in fan videos, match edits and group chats, repeated whenever Flamengo lose, concede late or miss an easy chance, and it remains popular because any rival supporter understands the joke immediately.