The bruh part comes from the long-running bruh meme reaction, a single flat word used online since the mid-2010s to mark disbelief or disappointment. Fart noises have an even older life as cheap, universal gag sounds in cartoons, pranks and early internet videos. Combining the two became a natural soundboard joke, pairing verbal judgement with a crude sound effect. It sits alongside the classic bruh reaction and variants like fart with reverb in meme collections, and it keeps circulating because the pairing is instantly readable in short edits, gaming clips and group chats.