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.