Bruh grew out of informal slang for brother, used as a laid-back address between friends before it became a shorthand reaction in online video. Short-form creators on Vine and later TikTok adopted the single-word clip as an easy way to signal disbelief, disappointment or secondhand embarrassment without explaining the joke. Because it is short, instantly recognisable and easy to drop over almost any fail, it spread through reaction videos, gaming edits and meme compilations, and it remains popular because one flat word can sum up a whole moment.