"My bad" is an informal expression used to admit a mistake or acknowledge that one has done something wrong. It is often said to take responsibility for an error or oversight, typically in a casual context.
The phrase "my bad" originated in American slang, which became popular in the 1980s. It is believed to have emerged from the sporting context, particularly in basketball, where players would acknowledge their errors. The term combines "my" as a possessive pronoun with "bad," meaning something undesirable or wrong.