“Bag” is common slang in the rap world. It has different meanings.
“Bag” might mean securing or winning over a partner or a significant other.
“I bagged my honey during our 3rd year of college and we have been together since.”
The term might also refer to having intercourse or sexual relations with someone.
“He was a playboy back in the day and bagged several beauties.”
More commonly, a bag is used to point to a large sum of money in physical form.
“Thieves in cartoons always got bags before getting thwarted by superheroes.”
Lastly, this slang might be used as the phrase “in the bag.” It means that you are in a zone where you are working at peak proficiency and focus.
“Jordan’s in the bag. Just hand him the ball and watch the highlight reel.”