As a piece of online slang, mentira, pô works as a compact way to accuse someone of lying without a long argument, which is why it travels well in short videos and messaging. The phrase pairs a direct word for a lie with pô, a casual Brazilian interjection that softens the charge into teasing rather than a serious dispute. That mix of challenge and humour has made it a go-to reaction for dubious stories, tall tales and playful boasts, especially where a creator wants the audience to instantly recognise disbelief in under two seconds.