The phrase comes from Among Us, the social deduction game released in 2018 that exploded in popularity during 2020. Players shortened suspicious to sus and used it to accuse the hidden impostor during emergency meetings. The specific wording when the impostor is sus spread as a copypasta and meme caption, often paired with distorted faces and ironic edits. Its deliberately broken grammar and the common misspelling inposter became part of the joke, helping the short clip survive as a standalone reaction long after peak Among Us streams faded.