I forgot about that. I thought it was popularized in the 90s by Bart Simpson.
To me, Bender telling Vernon to “eat my shorts” is unforgettable:
https://www.youtube.com/watch?v=Y5vCX8TGqmc&ab_channel=BellaM
Well, Bart is technically a Gen-Xer. He first appeared with his family in several short episodes on the Tracy Ulman show, the first short debuted on April 19, 1987. Bart is supposed to be 10 years old. So, he'd have been born in 1977. He uttered the phrase "Eat my shorts!" the first time in the second episode of the first season of The Simpsons (Bart the Genius), which aired January 14, 1990.