The line comes from Team Fortress 2, Valve's team-based multiplayer shooter released in 2007, where Scout is one of nine playable mercenaries. His voice lines, performed in a thick Boston accent, became widely shared as players clipped his taunts, thanks and insults for use outside the game. Thanks pally spread through TF2 gameplay videos, Garry's Mod animations and meme edits, where it became shorthand for a casual, cocky thank you. It remains popular because it is instantly recognisable, very short and easy to drop into almost any gaming moment.