Originally used to mean a young man, new to the game. By new to the game, I don’t mean he just meant a rapper, but he just started selling crack, just started rapping, whatever, but even simpler it was a term used to mean just a person much younger than you.

Now, commercial rappers have turned the meaning upside down to mean a ‘fine female’, apparently.
“shorty’s laugh was cold blooded as he spoke so foul,
Only twelve trying to tell me that he liked my style”
-NaS, 1994

“Shorty is shaking her ass on my Hummer with spinning rims, or something.”
-average commercialized rapper today
by Steelo J. May 21, 2005