I’ve only noticed “my bad” being used in the sense of "my mistake’ for the past year or two. It may have been in use for much longer, but since I don’t live in the U.S. I may have missed it.
Given that even Cecil is now using it, I’ve become curious about its origins.
A few questions:
How long has it been around?
What area/subculture did it originate in?
Was it popularized by a specific movie, TV show, or song?