An African-American phrase widely used in the midwest (circa '60-'70) usually meaning to take full responsibility for an incident or action. To apologize for a mistake.

The Michigan version of "my bad".
A mistake.

To not be of someone's 'thing,' interest, taste or expertise. A polite way of saying that you have no interest whatsoever in what is being suggested or discussed. Can also be used in admitting ignorance of a certain subject.

Compare 'bag' to cup of tea. Perhaps derived from 'bag of tea.'

The act of becoming one with whatever task you are trying to achieve. One dimensional. Tunnel vision. Grindin'. One who is "in my bag" has forgotten about all else except for the current moment. When you are in your bag you are unstoppable, you will shred anything and everything.

the act of being in your own world; focused; being in the zone; on your grind

be focased, you on your shit at the moment,
you making things happen.

When you're sad and are deep down in the feels usually about a relationship

The term "My Bag" was originally slang for taking responsibility for one's own actions. Somewhere in the early 90s people started saying "My bad" either because they wanted to change the verbage of the original, or because they just plain didn't understand the original meaning. "My Bag" is slang for "Baggage",ie: You take your own problems, put them in a bag and carry it on your own back. "It's on me, my fault, my problem. "My Bag" excepts and takes the burden, "My Bad" just dismisses it.

The term “my bag” was common from 1930 to about 1995. It means “my mistake, my fault, my apologies”. The popular term my bad is actually a 1980s mispronunciation of the term “my bag”.

“My bag” was a phrase used when playing a game of spades. In the game, you would have to for-tell how many "books" or hands you would take. If you went over that number it was called a "bag". If you were playing with a partner it was a courtesy to claim your mistake by saying "My Bag".

Spades came out of the Midwestern United States in the late 1930s. It was said to have been invented by college students who enjoyed both Whist and Bridge. They were looking for a fast-paced game that was competitive and strategic. The game slowly spread to other college campuses. It didn't really take off until WWII brought so much of America's youth into the military. Because the game was portable, could be played by small groups, and could often be played in less than twenty minutes, its popularity mushroomed. You can still find the game online.

“My Bag” meaning “My Mistake” should not be confused with “Not My Bag.” meaning “Not My Thing.” or “What's Your Bag?” meaning “What's Your Problem?”

When I was in high-school in the 70s “my bag” meaning “my fault” was very common. Even though “my bad” is said to have come out in the 80s I had never heard it until sometime around 2008 or so. I can't recall the last time I heard the term “My bag”.