The clip comes from Half Life, Valve's first person shooter series first released in 1998, where short pain vocalizations play when the player character or NPCs take damage. Those brief stock screams became familiar to a generation of PC players and were later ripped for soundboards and meme edits. The aargh survives online because it is generic enough to fit any hurt character while still being instantly recognizable to Half Life fans, and its extreme shortness makes it ideal for rapid fire editing.