Here's why it's called that:
* Antlers: Male deer grow antlers, which are bone structures that shed and regrow annually.
* Button Stage: In the early stages of antler development, they appear as small, hard, bony knobs called "buttons." These buttons are covered in a velvety skin called "velvet."
* "Button Buck": A "button buck" is a buck that is still in this early stage of antler growth and has only these small, bony buttons, not fully grown antlers.
Essentially, a button buck is a young male deer that hasn't quite reached maturity in terms of antler development.