work (one's) buns off

work (one's) buns off

To work really hard (on or at something). ("Buns" is a slang term for the buttocks.) I know you thought it was just a silly New Year's resolution, but I've been working my buns off at the gym! Sally and Jim work their buns off when we hold our consumer conference each year. I don't know what I'd do without them!
See also: buns, off, work
Farlex Dictionary of Idioms.

work one’s buns off

verb
See work one’s tail off
See also: buns, off, work
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • I've got work to do
  • go shares
  • off
  • offed
  • be at work
  • be your own master/mistress
  • mistress
  • be (one's) own master
  • hard work is not easy
  • off from work