Bruh grew out of African American Vernacular English slang for brother before becoming a staple reaction word across Vine, TikTok and YouTube, where short clips turned a single deadpan utterance into shorthand for disappointment. The sound spread because it needs no context: one word signals disbelief, secondhand embarrassment or a joke falling flat. Editors still reuse it in compilations, gaming highlights and prank reactions because it is instantly recognisable, easy to time and works across languages without translation.