The phrase comes from online chess culture, where sac is short for sacrifice and giving up a rook for a stronger attack is treated as a especially daring play. Clips of commentators reacting loudly to rook sacrifices spread widely on YouTube, TikTok and streaming highlights, and the stretched roooook delivery made this version easy to recognise and reuse. As chess content grew more meme driven, the shout escaped full game videos and became a standalone reaction for any risky trade that looks crazy but might be brilliant.