An
exclamation, usually mean spirited, that implies someone has made a mistake or misfortune has befell them.
Usually, it is used as a means to 'kick someone while they are down'
Buns can also be substituted for certain other slang terms.
For example, a person can say "my buns" implying the same thing as "my bad."
The term first became widely used in the
New York area and has since spread west.