Sofa Sunday
n. The Sunday after the United States Thanksgiving holiday, when people relax at home and purchase goods online or on TV.
Sofa Sunday is a real day, where everyone dresses up in impractical loungewear and goes shopping on their mobile devices. It's apparently the busiest online shopping day of the year, with most purchases being made between 9pm and 11pm.
The app Catalog Spree coined the term "Sofa Sunday" to refer to online shopping during the weekend after Thanksgiving, but before Cyber Monday.
—Kimberly Palmer, “Why You Should Stay Home on Black Friday,” U.S. News & World Report, November 21, 2012
2008 (earliest)
Cyber Monday is trying to cut into Black Friday. Why not create a Sofa Sunday television shopping day?
—Tim Rausch, “Why not Sofa Sunday for big deals?,” The Augusta Chronicle, December 22, 2008