Sup is short for what is up, a slang greeting that has circulated in online chat, gaming lobbies and short-form video for years as a quick, low-effort hello. Clips labelled with a number, like Sup 2, usually mark a later or alternate take shared on soundboards for creators who want a slightly different delivery without changing the joke. Its staying power comes from that simplicity: anyone can understand it instantly, it needs no context, and it works as a reaction, an entrance or a reply in memes, edits and streams.