The story
buck (in derogatory US sense of a black man) + breaking (as in breaking a horse)
First known use, by meaning
- from 21st century The act of publicly punishing a male slave, typically by flogging him, and in some cases subsequently sexually assaulting or raping him in front of other slaves, in order to humiliate him.
Etymology from Wiktionary, CC BY-SA 4.0.