A sarcastic thank you to someone who has wronged you. The expression dates to an early 2000's Star Wars related "Thank You George" campaign was started on the
internet and quickly spread through science fiction
fandom. The campaign centered around a web site that sold "Thank You George" t-shirts and merchandise. The web site turned out to be registered to a
game company called Decipher, who had produced a highly successful Star Wars collectible card
game between 1995 and
2001, only to have Lucasfilm pull the license in favor of Hasbro toys, who produced a new card
game that failed. The campaign seemed to have been started by Decipher as a way to profit from Star Wars without having to pay licensing, and a way to give George Lucas a sarcastic "thank you" after he killed Decipher's product in favor of Hasbro's product that failed.