The phrase comes from Neto, the former Brazilian footballer turned outspoken television commentator whose forceful delivery made many of his lines easy to clip and share. Num vai da is a colloquial shortening of não vai dar, meaning it will not work or it is not going to happen. Short excerpts like this spread widely through Brazilian meme pages, chats and soundboards, where a familiar voice can replace a longer reply. It remains popular because the meaning is clear even out of context and fits football talk, everyday plans and online arguments equally well.