The phrase comes from Brazilian Portuguese slang, where B.O. is short for boletim de ocorrência but is widely used in everyday speech to mean a problem, mess or awkward situation. Saying Eu não assumo esse B.O. is therefore a playful way of refusing to own someone else's trouble. The line circulates as a short reaction audio on Brazilian meme pages and soundboards, where its brevity makes it easy to reuse in edits, group chats and short videos. It stays popular because the situation it describes is universal, and the refusal is instantly understood even without translation.