The phrase comes from everyday French youth slang, where reuf is verlan for frère and the whole greeting is a familiar way to ask a close friend how they are doing. It has circulated widely in short online videos and meme edits, where creators use the brief spoken line as a recognisable hello rather than a formal greeting. Its popularity comes from that shared cultural shorthand: French-speaking audiences recognise it instantly, while others pick it up as a playful sound for friendship, humour and casual street culture.