The double donk comes from Team Fortress 2, where Demoman's Loose Cannon fires timed cannonballs that can be detonated in midair. Players began using double donk for the distinctive two-part hit sound, and clips of unlikely long-range shots helped the phrase spread through TF2 montages, streams and meme edits. It remains popular because the sound is instantly recognisable to TF2 players and works as shorthand for a skilful, lucky or absurdly well-timed hit.